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Monday, September 7, 2020

Avocado

From Wikipedia, the free encyclopedia
 
 
Avocado
Temporal range: 15–0 Ma Middle Miocene – Recent
Close-up picture of foliage and avocado fruit
Avocado fruit and foliage, Réunion island
Avocado with cross section edit.jpg
Scientific classification edit
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Magnoliids
Order: Laurales
Family: Lauraceae
Genus: Persea
Species:
P. americana
Binomial name
Persea americana
Synonyms
  • Laurus persea L.
  • Persea americana var. angustifolia Miranda
  • Persea americana var. drymifolia (Cham. & Schltdl.) S.F.Blake
  • Persea americana var. nubigena (L.O.Williams) L.E.Kopp
  • Persea drymifolia Cham. & Schltdl.
  • Persea edulis Raf.
  • Persea floccosa Mez
  • Persea gigantea L.O.Williams
  • Persea gratissima C.F.Gaertn.
  • Persea gratissima var. drimyfolia (Schltdl. & Cham.) Mez
  • Persea gratissima var. macrophylla Meisn.
  • Persea gratissima var. oblonga Meisn.
  • Persea gratissima var. praecox Nees
  • Persea gratissima var. vulgaris Meisn.
  • Persea leiogyna Blake
  • Persea nubigena L.O.Williams
  • Persea nubigena var. guatemalensis L.O.Williams
  • Persea paucitriplinervia Lundell
  • Persea persea (L.) Cockerell
  • Persea steyermarkii C.K.Allen 

The avocado (Persea americana), a tree likely originating from south-central Mexico, is classified as a member of the flowering plant family Lauraceae. The fruit of the plant, also called an avocado (or avocado pear or alligator pear), is botanically a large berry containing a single large seed.

Avocados are commercially valuable and are cultivated in tropical and Mediterranean climates throughout the world. They have a green-skinned, fleshy body that may be pear-shaped, egg-shaped, or spherical. Commercially, they ripen after harvesting. Avocado trees are partially self-pollinating, and are often propagated through grafting to maintain predictable fruit quality and quantity. In 2017, Mexico produced 34% of the world supply of avocados.

Botany

Persea americana is a tree that grows to 20 m (66 ft), with alternately arranged leaves 12–25 cm (5–10 in) long. Panicles of flowers with deciduous bracts arise from new growth or the axils of leaves. The flowers are inconspicuous, greenish-yellow, 5–10 mm (31638 in) wide.

The species is variable because of selection pressure by humans to produce larger, fleshier fruits with a thinner exocarp. The avocado fruit is a climacteric, single-seeded berry, due to the imperceptible endocarp covering the seed, rather than a drupe. The pear-shaped fruit is usually 7–20 cm (3–8 in) long, weighs between 100 and 1,000 g (3 12 and 35 12 oz), and has a large central seed, 5–6.4 cm (2–2 12 in) long.

History

Native Oaxaca criollo avocados, the ancestral form of today's domesticated varieties
 
Persea americana, or the avocado, possibly originated in the Tehuacan Valley in the state of Puebla, Mexico, although fossil evidence suggests similar species were much more widespread millions of years ago. However, there is evidence for three possible separate domestications of the avocado, resulting in the currently recognized Mexican (aoacatl), Guatemalan (quilaoacatl), and West Indian (tlacacolaocatl) landraces. The Mexican and Guatemalan landraces originated in the highlands of those countries, while the West Indian landrace is a lowland variety that ranges from Guatemala, Costa Rica, Colombia, Ecuador to Peru, achieving a wide range through human agency before the arrival of the Europeans. The three separate landraces were most likely to have already intermingled in pre-Columbian America and were described in the Florentine Codex.

The earliest residents were living in temporary camps in an ancient wetland eating avocados, chilies, mollusks, sharks, birds, and sea lions. The oldest discovery of an avocado pit comes from Coxcatlan Cave, dating from around 9,000 to 10,000 years ago. Other caves in the Tehuacan Valley from around the same time period also show early evidence for the presence and consumption of avocado. There is evidence for avocado use at Norte Chico civilization sites in Peru by at least 3,200 years ago and at Caballo Muerto in Peru from around 3,800 to 4,500 years ago.

The native, undomesticated variety is known as a criollo, and is small, with dark black skin, and contains a large seed. It probably coevolved with extinct megafauna. The avocado tree also has a long history of cultivation in Central and South America, likely beginning as early as 5,000 BC. A water jar shaped like an avocado, dating to AD 900, was discovered in the pre-Incan city of Chan Chan.

The earliest known written account of the avocado in Europe is that of Martín Fernández de Enciso (circa 1470–1528) in 1519 in his book, Suma De Geographia Que Trata De Todas Las Partidas Y Provincias Del Mundo. The first detailed account that unequivocally describes the avocado was given by Gonzalo Fernández de Oviedo y Valdés in his work Sumario de la natural historia de las Indias [es] in 1526. The first written record in English of the use of the word 'avocado' was by Hans Sloane, who coined the term, in a 1696 index of Jamaican plants. The plant was introduced to Spain in 1601, Indonesia around 1750, Mauritius in 1780, Brazil in 1809, the United States mainland in 1825, South Africa and Australia in the late 19th century, and the Ottoman Empire in 1908. In the United States, the avocado was introduced to Florida and Hawaii in 1833 and in California in 1856.

Before 1915, the avocado was commonly referred to in California as ahuacate and in Florida as alligator pear. In 1915, the California Avocado Association introduced the then-innovative term avocado to refer to the plant.

Etymology

The word "avocado" comes from the Spanish aguacate, which in turn comes from the Nahuatl word āhuacatl [aːˈwakat͡ɬ], which goes back to the proto-Aztecan *pa:wa which also meant "avocado". Sometimes the Nahuatl word was used with the meaning "testicle", probably because of the likeness between the fruit and the body part.

The modern English name comes from an English rendering of the Spanish aguacate as avogato. The earliest known written use in English is attested from 1697 as "avogato pear", a term which was later corrupted as "alligator pear". Because the word avogato sounded like "advocate", several languages reinterpreted it to have that meaning. French uses avocat, which also means lawyer, and "advocate" — forms of the word appear in several Germanic languages, such as the (now obsolete) German Advogato-Birne, the old Danish advokat-pære (today it is called avocado) and the Dutch advocaatpeer.

Regional names

In other Central American and Caribbean Spanish-speaking countries, it is known by the Mexican name, while South American Spanish-speaking countries use a Quechua-derived word, palta. In Portuguese, it is abacate. The fruit is sometimes called an avocado pear or alligator pear (due to its shape and the rough green skin of some cultivars). The Nahuatl āhuacatl can be compounded with other words, as in ahuacamolli, meaning avocado soup or sauce, from which the Spanish word guacamole derives.

In the United Kingdom, the term avocado pear is still sometimes misused as applied when avocados first became commonly available in the 1960s.

Originating as a diminutive in Australian English, a clipped form, avo, has since become a common colloquialism in South Africa and the United Kingdom. 

It is known as "butter fruit" in parts of India.

Cultivation

Persea americana, young avocado plant (seedling), complete with parted pit and roots
 
The subtropical species needs a climate without frost and with little wind. High winds reduce the humidity, dehydrate the flowers, and affect pollination. When even a mild frost occurs, premature fruit drop may occur, although the 'Hass' cultivar can tolerate temperatures down to −1 °C. Several cold-hardy varieties are planted in the region of Gainesville, Florida, which survive temperatures as low as −6.5 °C (20 °F) with only minor leaf damage. The trees also need well-aerated soils, ideally more than 1 m deep.

According to information published by the Water Footprint Network, it takes an average of approximately 70 litres (18 US gallons) of applied fresh ground or surface water, not including rainfall or natural moisture in the soil, to grow one avocado. However, the amount of water needed depends on where it is grown; for example, in the main avocado-growing region of Chile, about 320 L (85 US gal) of applied water are needed to grow one avocado.

Yield is reduced when the irrigation water is highly saline.

Harvest and postharvest

Commercial orchards produce an average of seven tonnes per hectare each year, with some orchards achieving 20 tonnes per hectare. Biennial bearing can be a problem, with heavy crops in one year being followed by poor yields the next.

Like the banana, the avocado is a climacteric fruit, which matures on the tree, but ripens off the tree. Avocados used in commerce are picked hard and green and kept in coolers at 3.3 to 5.6 °C (37.9 to 42.1 °F) until they reach their final destination. Avocados must be mature to ripen properly. Avocados that fall off the tree ripen on the ground. Generally, the fruit is picked once it reaches maturity; Mexican growers pick 'Hass' avocados when they have more than 23% dry matter, and other producing countries have similar standards. Once picked, avocados ripen in one to two weeks (depending on the cultivar) at room temperature (faster if stored with other fruits such as apples or bananas, because of the influence of ethylene gas). Some supermarkets sell ripened avocados which have been treated with synthetic ethylene to hasten ripening. The use of an ethylene gas "ripening room", which is now an industry standard, was pioneered in the 1980s by farmer Gil Henry of Escondido, California, in response to footage from a hidden supermarket camera which showed shoppers repeatedly squeezing hard, unripe avocados, putting them "back in the bin," and moving on without making a purchase. In some cases, avocados can be left on the tree for several months, which is an advantage to commercial growers who seek the greatest return for their crop, but if the fruit remains unpicked for too long, it falls to the ground.

Breeding

A seedless avocado, or cuke, growing next to two regular avocados
 
The species is only partially able to self-pollinate because of dichogamy in its flowering. This limitation, added to the long juvenile period, makes the species difficult to breed. Most cultivars are propagated by grafting, having originated from random seedling plants or minor mutations derived from cultivars. Modern breeding programs tend to use isolation plots where the chances of cross-pollination are reduced. That is the case for programs at the University of California, Riverside, as well as the Volcani Centre and the Instituto de Investigaciones Agropecuarias in Chile.

The avocado is unusual in that the timing of the male and female flower phases differs among cultivars. The two flowering types are A and B. A-cultivar flowers open as female on the morning of the first day and close in late morning or early afternoon. Then they open as male in the afternoon of the second day. B varieties open as female on the afternoon of the first day, close in late afternoon and reopen as male the following morning.
  • A cultivars: 'Hass', 'Gwen', 'Lamb Hass', 'Pinkerton', 'Reed'
  • B cultivars: 'Fuerte', 'Sharwil', 'Zutano', 'Bacon', 'Ettinger', 'Sir Prize', 'Walter Hole'
Certain cultivars, such as the 'Hass', have a tendency to bear well only in alternate years. After a season with a low yield, due to factors such as cold (which the avocado does not tolerate well), the trees tend to produce abundantly the next season. In addition, due to environmental circumstances during some years, seedless avocados may appear on the trees. Known in the avocado industry as "cukes", they are usually discarded commercially due to their small size.

Propagation and rootstocks

A common technique to germinate avocados at home is to poke the avocado with toothpicks and leave it partially submerged in indirect light
 
A young avocado sprout

Avocados can be propagated by seed, taking roughly four to six years to bear fruit, although in some cases seedlings can take 10 years to come into bearing. The offspring is unlikely to be identical to the parent cultivar in fruit quality. Prime quality varieties are therefore propagated by grafting to rootstocks that are propagated by seed (seedling rootstocks) or by layering (clonal rootstocks). After about a year of growing in a greenhouse, the young rootstocks are ready to be grafted. Terminal and lateral grafting is normally used. The scion cultivar grows for another 6–12 months before the tree is ready to be sold. Clonal rootstocks are selected for tolerance of specific soil and disease conditions, such as poor soil aeration or resistance to the soil-borne disease (root rot) caused by Phytophthora

Commercial avocado production is limited to a small fraction of the vast genetic diversity in the species. Conservation of this genetic diversity has relied largely on field collection, as avocado seeds often do not survive storage in seed banks. This is problematic, as field preservation of living cultivars is expensive, and habitat loss threatens wild cultivars. More recently, an alternate method of conservation has been developed based on cryopreservation of avocado somatic embryos with reliable methods for somatic embryogenesis and reconstitution into living trees.

Growing indoors

Indoors, an avocado tree is usually grown from the pit of an avocado fruit. This is often done by removing the pit from a ripe, unrefrigerated avocado fruit. The pit is then stabbed with three or four toothpicks, about one-third of the way up from the flat end. The pit is placed in a jar or vase containing tepid water. It should split in four to six weeks and yield roots and a sprout. If there is no change by this time, the avocado pit is discarded. Once the stem has grown a few inches, it is placed in a pot with soil. It should be watered every few days. Avocados have been known to grow large, so owners must be ready to re-pot the plant several times.

Pests and diseases

P. americana, avocado plant flowers
 
Avocado trees are vulnerable to bacterial, viral, fungal, and nutritional diseases (excesses and deficiencies of key minerals). Disease can affect all parts of the plant, causing spotting, rotting, cankers, pitting, and discoloration. The pyriform scale insect (Protopulvinaria pyriformis) is known from Australia, South Africa, Israel, Italy, France, Spain, Cuba, Florida, and Peru. It is normally found on avocado, and in Peru it is said to be the worst insect pest of the fruit. Certain cultivars of avocado seem more susceptible to attack by the scale than others.

Cultivation in Mexico

Mexico is by far the world's largest avocado growing country, producing several times more than the second largest producer. In 2013, the total area dedicated to avocado production was 188,723 hectares (415,520 acres), and the harvest was 2.03 million tonnes in 2017.  The states that produce the most are México, Morelos, Nayarit, Puebla, and Michoacan, accounting for 86% of the total. In Michoacán, the cultivation is complicated by the existence of drug cartels that extort protection fees from cultivators. They are reported to exact 2000 Mexican pesos per hectare from avocado farmers and 1 to 3 pesos/kg of harvested fruit.

Cultivation in California

The avocado was introduced from Mexico to California in the 19th century, and has become a successful cash crop. About 24,000 hectares (59,000 acres) – some 95% of United States avocado production – is located in Southern California, with 60% in San Diego County.  Fallbrook, California, claims, without official recognition, the title of "Avocado Capital of the World" (also claimed by the town of Uruapan in Mexico), and both Fallbrook and Carpinteria, California, host annual avocado festivals. Avocado is the official fruit of the state of California.

Cultivation in Peru

'Hass' avocado production in Peru encompasses thousands of hectares in central and western Peru. Peru has now become the largest supplier of avocados imported to the European Union and the second largest supplier to Asia and the United States. Peru's location near the equator and along the Pacific Ocean creates consistently mild temperatures all year.

'Hass' avocados from Peru are seasonally available to consumers from May through September and are promoted under the auspices of the Peruvian Avocado Commission, headquartered in Washington, D.C.

A cultivars

Avocado 'Choquette' grafted
 
A seedling from Miami, Florida. 'Choquette' bore large fruit of good eating quality in large quantities and had good disease resistance, and thus became a major cultivar. Today 'Choquette' is widely propagated in south Florida both for commercial growing and for home growing.
'Gwen'
A seedling bred from 'Hass' x 'Thille' in 1982, 'Gwen' is higher yielding and more dwarfing than 'Hass' in California. The fruit has an oval shape, slightly smaller than 'Hass' (100–200 g or 3 12–7 oz), with a rich, nutty flavor. The skin texture is more finely pebbled than 'Hass', and is dull green when ripe. It is frost-hardy down to −1 °C (30 °F).
'Hass'
Two 'Hass' avocados
 
The 'Hass' is the most common cultivar of avocado. It produces fruit year-round and accounts for 80% of cultivated avocados in the world. All 'Hass' trees are descended from a single "mother tree" raised by a mail carrier named Rudolph Hass, of La Habra Heights, California. Hass patented the productive tree in 1935. The "mother tree", of uncertain subspecies, died of root rot and was cut down in September 2002. 'Hass' trees have medium-sized (150–250 g or 5 12–9 oz), ovate fruit with a black, pebbled skin. The flesh has a nutty, rich flavor with 19% oil. A hybrid Guatemalan type can withstand temperatures to −1 °C (30 °F).
'Lula'
A seedling reportedly grown from a 'Taft' avocado planted in Miami on the property of George Cellon, it is named after Cellon's wife, Lula. It was likely a cross between Mexican and Guatemalan types. 'Lula' was recognized for its flavor and high oil content and propagated commercially in Florida. It is also very commonly used as a rootstock for nursery production, and is hardy to −4 °C (25 °F).
'Maluma'
A relatively new cultivar, it was discovered in South Africa in the early 1990s by Mr. A.G. (Dries) Joubert. It is a chance seedling of unknown parentage.
'Pinkerton'
First grown on the Pinkerton Ranch in Saticoy, California, in the early 1970s, 'Pinkerton' is a seedling of 'Hass' x 'Rincon'. The large fruit has a small seed, and its green skin deepens in color as it ripens. The thick flesh has a smooth, creamy texture, pale green color, good flavor, and high oil content. It shows some cold tolerance, to −1 °C (30 °F) and bears consistently heavy crops. A hybrid Guatemalan type, it has excellent peeling characteristics.
'Reed'
Developed from a chance seedling found in 1948 by James S. Reed in California, this cultivar has large, round, green fruit with a smooth texture and dark, thick, glossy skin. Smooth and delicate, the flesh has a slightly nutty flavor. The skin ripens green. A Guatemalan type, it is hardy to −1 °C (30 °F). Tree size is about 5 by 4 m (16 12 by 13 ft).

B cultivars

Avocado fruit (cv. 'Fuerte'); left: whole, right: in section
'Bacon'
Developed by a farmer, James Bacon, in 1954, Bacon has medium-sized fruit with smooth, green skin with yellow-green, light-tasting flesh. When ripe, the skin remains green, but darkens slightly, and fruit yields to gentle pressure. It is cold-hardy down to −5 °C (23 °F).
'Brogden'
Possibly a cross between Mexican and West Indian types, 'Brogden' originated as a seedling grown in Winter Haven, Florida, on the property of Tom W. Brogden. The variety was recognized for its cold-hardiness to −5 °C (23 °F) and became commercially propagated as nursery stock for home growing. It is noted for its dark purple skin at maturity.
'Cleopatra'
Heavy flowering. In cooler climates opening and closing of the flower tends to overlap making them more self-fertile. Medium-sized pear shaped black fruit with a shiny skin, larger than Hass. Yellow creamy flesh of creamy rich flavour. The skin turns black prior to harvest. Tree size 3m x 3m, marketed as dwarf.
'Ettinger'
A Mexican-Guatemalan cross seedling of 'Fuerte', this cultivar originated in Israel, and was put into production there in 1947. Mature trees tolerate four hours at −6 °C (21 °F). The fruit has a smooth, thin, green skin that does not peel easily. The flesh is very pale green.
'Fuerte'
A Mexican-Guatemalan cross originating in Puebla, the 'Fuerte' earned its name, which means strong in Spanish, after it withstood a severe frost in California in 1913. Hardy to −3 °C (27 °F), it has medium-sized, pear-shaped fruit with a green, leathery, easy-to-peel skin. The creamy flesh of mild and rich flavor has 18% oil. The skin ripens green. Tree size is 6 by 4 m (19 12 by 13 ft).
'Monroe'
A Guatemalan/West Indian cross that originated from a seedling grown in Homestead, Florida, on the property of J.J.L. Phillips, 'Monroe' was patented in 1937 and became a major commercial cultivar due to its cold hardiness and production qualities. The fruit is large, averaging over 900 g (2 lb) in weight, has an elliptical shape, and green, glossy skin. Hardy to −3 °C (27 °F).
'Sharwil'
Predominantly Guatemalan, with some Mexican race genes, 'Sharwil' was developed in 1951 by Sir Frank Sharpe at Redland Bay, southern Queensland. The name "Sharwil" is an amalgamation of Sharpe and Wilson (J.C. Wilson being the first propagator). Scions were sent from Australia to Hawaii in 1966. A medium-sized fruit with rough green skin, it closely resembles the 'Fuerte', but is slightly more oval in shape. The fruit has greenish-yellow flesh with a rich, nutty flavor and high oil content (20–24%), and a small seed. The skin is green when ripe. It represents more than 57% of the commercial farming in Hawaii, and represents up to 20% of all avocados grown in New South Wales, Australia. It is a regular and moderate bearer with excellent quality fruit, but is sensitive to frost. Disease and pest resistance are superior to 'Fuerte'.
'Zutano'
Originated by R.L. Ruitt in Fallbrook in 1926, this Mexican variety is hardy to −4 °C (25 °F). The large, pear-shaped fruit has a shiny, thin, yellow-green skin that peels moderately easily. The flesh is pale green with fibers and has a light flavor.

Other cultivars

Other avocado cultivars include 'Spinks'. Historically attested varieties (which may or may not survive among horticulturists) include the 'Challenge', 'Dickinson', 'Kist', 'Queen', 'Rey', 'Royal', 'Sharpless', and 'Taft'.

Stoneless avocado

A stoneless avocado, marketed as a "cocktail avocado," which does not contain a pit, is available on a limited basis. They are five to eight centimetres long; the whole fruit may be eaten, including the skin. It is produced from an unpollinated blossom in which the seed does not develop. Seedless avocados regularly appear on trees. Known in the avocado industry as "cukes", they are usually discarded commercially due to their small size.

Production

Avocado production – 2017
Country Production (millions of tonnes)
 Mexico
2.01
 Dominican Republic
0.64
 Peru
0.47
 Indonesia
0.36
 Colombia
0.31
World
5.92
Source: FAOSTAT of the United Nations
In 2017, world production of avocados was 5.9 million tonnes, led by Mexico with 34% (2.01 million tonnes) of the total (table). Other major producers were Dominican Republic, Peru, Indonesia, and Colombia, together producing 30% of the world total (table).[44] In 2018, the US Department of Agriculture estimated that 231,028 hectares (570,880 acres) in total were under cultivation for avocado production in Mexico, a 6% increase over the previous year, and that 2 million tonnes would be exported.[58] The Mexican state of Michoacán is the world leader in avocado production, accounting for 80% of all Mexican output.[58] Most Mexican growers produce the Hass variety due to its high demand worldwide and longer shelf life.[58]

Avocado-related international trade issues

First international air shipment of avocados from Los Angeles, California, to Toronto, Ontario, for the Canadian National Exhibition
 
After the North American Free Trade Agreement (NAFTA) went into effect in 1994, Mexico tried exporting avocados to the US. The US government resisted, claiming the trade would introduce Tephritidae fruit flies that would destroy California's crops. The Mexican government responded by inviting USDA inspectors to Mexico, but the US government declined, claiming fruit fly inspection was not feasible. The Mexican government then proposed to sell avocados only to the northeastern US in the winter (fruit flies cannot withstand extreme cold). The US government continued to resist, but agreed after the Mexican government started erecting barriers to US corn.

Selling avocados in Santo Domingo, Dominican Republic. The sign "H2O KT" is a play on aguacate, the Spanish word for avocado.
 
Imports from Mexico in the 2005–2006 season exceeded 130,000 metric tons (143,000 short tons; 128,000 long tons).

In 2009, Peru joined Chile and Mexico as an exporter of avocados to the US.

In the US, avocados are grown in California and Florida, where land, labor, and water are expensive. Avocado trees require frequent, deep watering to bear optimally, particularly in spring, summer, and fall. Due to increased Southern California water costs, they are now costly to grow. California produces 90% of the United States' avocados.

As of 2013, Mexico leads international exports, with other significant production in California, New Zealand, Peru, and South Africa.

During the coronavirus pandemic, Mexican avocado farmers slowed harvesting thinking that consumption would drop. In fact, there was a surge in demand causing prices to rise as well.

Culinary uses

Avocado salad, and a tomato and black olive salsa, on a toasted baguette
 
The fruit of horticultural cultivars has a markedly higher fat content than most other fruit, mostly monounsaturated fat, and as such serves as an important staple in the diet of consumers who have limited access to other fatty foods (high-fat meats and fish, dairy products). Having a high smoke point, avocado oil is expensive compared to common salad and cooking oils, and is mostly used for salads or dips

A ripe avocado yields to gentle pressure when held in the palm of the hand and squeezed. The flesh is prone to enzymatic browning, quickly turning brown after exposure to air. To prevent this, lime or lemon juice can be added to avocados after peeling. 

Indonesian-style avocado milkshake with chocolate syrup
 
The fruit is not sweet, but distinctly and subtly flavored, with smooth texture. It is used in both savory and sweet dishes, though in many countries not for both. The avocado is common in vegetarian cuisine as a substitute for meats in sandwiches and salads because of its high fat content. 

Generally, avocado is served raw, though some cultivars, including the common 'Hass', can be cooked for a short time without becoming bitter. The flesh of some avocados may be rendered inedible by heat. Prolonged cooking induces this chemical reaction in all cultivars.

A guacamole mix (right) used as a dip for tortilla chips (left).
 
Sliced avocado
 
Unusual avocado variety from Cebu, Philippines
 
It is used as the base for the Mexican dip known as guacamole, as well as a spread on corn tortillas or toast, served with spices.




In the Philippines, Brazil, Indonesia, Vietnam, and southern India (especially the coastal Kerala, Tamil Nadu and Karnataka region), avocados are frequently used for milkshakes and occasionally added to ice cream and other desserts. In Brazil, Vietnam, the Philippines and Indonesia, a dessert drink is made with sugar, milk or water, and pureed avocado. Chocolate syrup is sometimes added. In Morocco, a similar chilled avocado and milk drink is sweetened with confectioner's sugar and flavored with a touch of orange flower water


In Ethiopia, avocados are made into juice by mixing them with sugar and milk or water, usually served with Vimto and a slice of lemon. It is also common to serve layered multiple fruit juices in a glass (locally called Spris) made of avocados, mangoes, bananas, guavas, and papayas. Avocados are also used to make salads. 

Avocados in savory dishes, often seen as exotic, are a relative novelty in Portuguese-speaking countries, such as Brazil, where the traditional preparation is mashed with sugar and lime, and eaten as a dessert or snack. This contrasts with Spanish-speaking countries such as Chile, Mexico, or Argentina, where the opposite is true and sweet preparations are rare.




In Australia and New Zealand, avocados are commonly served on sandwiches, sushi, toast, or with chicken. In Ghana, they are often eaten alone on sliced bread as a sandwich. In Sri Lanka, their well-ripened flesh, thoroughly mashed or pureed with milk and kitul treacle (a liquid jaggery made from the sap of the inflorescence of jaggery palms), is a common dessert. In Haiti, they are often consumed with cassava or regular bread for breakfast.


In Mexico and Central America, avocados are served mixed with white rice, in soups, salads, or on the side of chicken and meat. They are also commonly added to pozole. In Peru, they are consumed with tequeños as mayonnaise, served as a side dish with parrillas, used in salads and sandwiches, or as a whole dish when filled with tuna, shrimp, or chicken. In Chile, it is used as a puree-like sauce with chicken, hamburgers, and hot dogs; and in slices for celery or lettuce salads. The Chilean version of Caesar salad contains large slices of mature avocado. In Kenya and Nigeria, the avocado is often eaten as a fruit alone or mixed with other fruits in a fruit salad, or as part of a vegetable salad. 

Avocado is a primary ingredient in avocado soup. Avocado slices are frequently added to hamburgers, tortas, hot dogs, and carne asada. Avocado can be combined with eggs (in scrambled eggs, tortillas, or omelettes), and is a key ingredient in California rolls and other makizushi ("maki", or rolled sushi).

In the United Kingdom, the avocado became available during the 1960s when introduced by Sainsbury's under the name 'avocado pear'.

Leaves

In addition to the fruit, the leaves of Mexican avocados (Persea americana var. drymifolia) are used in some cuisines as a spice, with a flavor somewhat reminiscent of anise. They are sold both dried and fresh, toasted before use, and either crumbled or used whole, commonly in bean dishes. Leaves of P. americana, Guatemalan variety, are toxic to goats, sheep, and horses.

Nutritional value

Avocados, raw
Nutritional value per 100 g (3.5 oz)
Energy670 kJ (160 kcal)

8.53 g
Sugars0.66 g
Dietary fiber6.7 g

14.66 g
Saturated2.13 g
Monounsaturated9.80 g
Polyunsaturated1.82 g

2 g

VitaminsQuantity %DV
Vitamin A equiv.
1%
7 μg
1%
62 μg
271 μg
Thiamine (B1)
6%
0.067 mg
Riboflavin (B2)
11%
0.13 mg
Niacin (B3)
12%
1.738 mg
Pantothenic acid (B5)
28%
1.389 mg
Vitamin B6
20%
0.257 mg
Folate (B9)
20%
81 μg
Vitamin C
12%
10 mg
Vitamin E
14%
2.07 mg
Vitamin K
20%
21 μg

MineralsQuantity %DV
Calcium
1%
12 mg
Iron
4%
0.55 mg
Magnesium
8%
29 mg
Manganese
7%
0.142 mg
Phosphorus
7%
52 mg
Potassium
10%
485 mg
Sodium
0%
7 mg
Zinc
7%
0.64 mg

Other constituentsQuantity
Water73.23 g
Fluoride7 µg
Beta-sitosterol76 mg

Percentages are roughly approximated using US recommendations for adults.
Source: USDA Nutrient Database

Nutrients and fat composition

A typical serving of avocado (100 g) is moderate to rich in several B vitamins and vitamin K, with good content of vitamin C, vitamin E and potassium (right table, USDA nutrient data). Avocados also contain phytosterols and carotenoids, such as lutein and zeaxanthin.

Avocados have diverse fats. For a typical avocado:
Although costly to produce, nutrient-rich avocado oil has diverse uses for salads or cooking and in cosmetics and soap products. Avocados are also a good source of vitamins B, E, and C, copper and fiber; their potassium content is higher than bananas.

As a houseplant

Avocado houseplant leaf with ruler to indicate size.
 
The avocado tree can be grown domestically and used as a decorative houseplant. The pit germinates in normal soil conditions or partially submerged in a small glass (or container) of water. In the latter method, the pit sprouts in four to six weeks, at which time it is planted in standard houseplant potting soil. The plant normally grows large enough to be prunable; it does not bear fruit unless it has ample sunlight. Home gardeners can graft a branch from a fruit-bearing plant to speed maturity, which typically takes four to six years to bear fruit.

Allergies

Some people have allergic reactions to avocado. There are two main forms of allergy: those with a tree-pollen allergy develop local symptoms in the mouth and throat shortly after eating avocado; the second, known as latex-fruit syndrome, is related to latex allergy and symptoms include generalised urticaria, abdominal pain, and vomiting and can sometimes be life-threatening.

Toxicity to animals

Avocado leaves, bark, skin, or pit are documented to be harmful to animals; cats, dogs, cattle, goats, rabbits, rats, guinea pigs, birds, fish, and horses can be severely harmed or even killed when they consume them. The avocado fruit is poisonous to some birds, and the American Society for the Prevention of Cruelty to Animals (ASPCA) lists it as toxic to horses.

Avocado leaves contain a toxic fatty acid derivative, persin, which in sufficient quantity can cause colic in horses and without veterinary treatment, death. The symptoms include gastrointestinal irritation, vomiting, diarrhea, respiratory distress, congestion, fluid accumulation around the tissues of the heart, and even death. Birds also seem to be particularly sensitive to this toxic compound. A line of premium dog and cat food, AvoDerm, uses oils and meal made from avocado meat as main ingredients. The manufacturer says the avocado's leaves and pit are the source of toxicity, and only in the Guatemalan variety of avocados, and the fruit is often eaten by orchard dogs as well as wildlife such as bears and coyotes.

Coevolution

In 1982, evolutionary biologist Daniel H. Janzen concluded that the avocado is an example of an 'evolutionary anachronism', a fruit adapted for ecological relationship with now-extinct large mammals (such as giant ground sloths or gomphotheres). Most large fleshy fruits serve the function of seed dispersal, accomplished by their consumption by large animals. There are some reasons to think that the fruit, with its mildly toxic pit, may have coevolved with Pleistocene megafauna to be swallowed whole and excreted in their dung, ready to sprout. No extant native animal is large enough to effectively disperse avocado seeds in this fashion.

Spring house

From Wikipedia, the free encyclopedia
 
A spring house, or springhouse, is a small building, usually of a single room, constructed over a spring. While the original purpose of a springhouse was to keep the spring water clean by excluding fallen leaves, animals, etc., the enclosing structure was also used for refrigeration before the advent of ice delivery and, later, electric refrigeration. The water of the spring maintains a constant cool temperature inside the spring house throughout the year. Food that would otherwise spoil, such as meat, fruit, or dairy products, could be kept there, safe from animal depredations as well. Springhouses thus often also served as pumphouses, milkhouses, and root cellars.

The Tomahawk Spring spring house at Tomahawk, West Virginia, was listed on the National Register of Historic Places in 1994.

Long Now Foundation

From Wikipedia, the free encyclopedia
 
The Long Now Foundation
2006-08-15 - United States - California - San Francisco - Sign - Long Now.jpg
FoundedJanuary 4, 1996; 24 years ago
Type501(c)(3)
68-0384748
Registration no.C1956835
Location
Coordinates37.8064591°N 122.4321258°WCoordinates: 37.8064591°N 122.4321258°W
Key people
President Stewart Brand, Brian Eno
Websitelongnow.org

The Long Now Foundation, established in 1996, is an American public non-profit organization based in San Francisco that seeks to start and promote a long-term cultural institution. It aims to provide a counterpoint to what it views as today's "faster/cheaper" mindset and to promote "slower/better" thinking. The Long Now Foundation hopes to "creatively foster responsibility" in the framework of the next 10,000 years. In a manner somewhat similar to the Holocene calendar, the foundation uses 5-digit dates to address the Year 10,000 problem (e.g., by writing the current year "02020" rather than "2020"). The organisation's logo is X, a capital X with an overline, a representation of 10,000 in Roman numerals.

Brian Eno, Danny Hillis, and Stewart Brand speaking at "The Long Now, now" – an event in January 2014 at the Palace of Fine Arts in San Francisco.

Projects

The foundation has several ongoing projects, including a 10,000-year clock known as the Clock of the Long Now, the Rosetta Project, the Long Bet Project, the open source Timeline Tool (also known as Longviewer), the Long Server and a monthly seminar series.

Clock of the Long Now

The purpose of the Clock of the Long Now is to construct a timepiece that will operate with minimum human intervention for ten millennia. It is to be constructed of durable materials, to be easy to repair, and to be made of largely valueless materials in case knowledge of the clock is lost or it is deemed to be of no value to an individual or possible future civilization; in this way it is hoped that the Clock will not be looted or destroyed. Its power source (or sources) should be renewable but similarly unlootable. A prototype of a potential final clock candidate was activated on December 31, 1999, and is currently on display at the Science Museum in London. The Foundation is currently building the Clock of the Long Now in Van Horn, Texas. The project has no expected completion date. "If it's finished in my lifetime we're doing it wrong," said project director Alexander Rose.

Rosetta Project

The Rosetta Project is an effort to preserve all languages that have a high likelihood of extinction over the period from 2000 to 2100. These include many languages whose native speakers number in the thousands or fewer. Other languages with many more speakers are considered by the project to be endangered because of the increasing importance of English as an international language of commerce and culture. Samples of such languages are to be inscribed onto a disc of nickel alloy three inches (7.62 cm) across. A Version 1.0 of the disc was completed on November 3, 2008.

Long Bet Project

The Long Bet Project was created by The Long Now Foundation to propose and keep track of bets on long-term events and stimulate discussion about the future. The Long Now Foundation describes The Long Bet Project as a "public arena for enjoyably competitive predictions, of interest to society, with philanthropic money at stake." One example bet would be on whether people will regularly fly on pilotless aircraft by 2030. 

Bets that were resolved in 2010 included predictions about peak oil, print on demand, modem obsolescence, and commercially available 100-qubit quantum computers.

An analysis by researcher Gwern Branwen found dozens of bets that had already expired but had not resolved, and many others with poorly defined resolution criteria. Branwen also found that the vast majority of the expired predictions resolved false, so that anyone could make a profit by betting indiscriminately against existing predictions. In light of these and other issues, and the website’s extremely low activity levels (with an average of less than two bets per year), Branwen concluded that the Long Bet Project should be shut down.

Seminars about long-term thinking

In November 2003, The Long Now Foundation began a series of monthly seminars about long-term thinking (SALT) with a lecture by Brian Eno. The seminars are held in the San Francisco Bay Area and have focused on long-term policy and thinking, scenario planning, singularity and the projects of the foundation. The seminars are available for download in various formats from The Long Now Foundation. They are intended to "nudge civilization toward making long-term thinking automatic and common". Topics have included preserving environmental resources, the deep past and deep future of the sciences and the arts, human life extension, the likelihood of an asteroid strike in the future, SETI, and the nature of time.

Long Now Foundation debate format

As part of the seminar series, there are occasionally debates on areas of long term concern, such as synthetic biology or "historian vs futurist on human progress".

The point of Long Now debates is not win-lose. The point is public clarity and deep understanding, leading to action graced with nuance and built-in adaptivity, with long-term responsibility in mind.

In operation, "There are two debaters, Alice and Bob. Alice takes the podium, makes her argument. Then Bob takes her place, but before he can present his counter-argument, he must summarize Alice's argument to her satisfaction — a demonstration of respect and good faith. Only when Alice agrees that Bob has got it right is he permitted to proceed with his own argument — and then, when he's finished, Alice must summarize it to his satisfaction."

Mutual understanding is enforced by a reciprocal requirement to describe the other's argument to their satisfaction, with the goal being more understanding after the event than there was beforehand.

The Interval

The Interval bar in Fort Mason, San Francisco
 
Opened in June 2014, The Interval was designed as social space in the foundation's Fort Mason facility in San Francisco. The purpose of The Interval is to have a public space where people can come together to discuss ideas and topics related to long-term thinking, as well as provide a venue for a variety of Long Now events. The Interval includes lounge furniture, artifacts from the foundation's projects, a library, audio/video equipment, and a bar serving tea and coffee during the day, and cocktails during the night. In October 2014 The Interval was named by Thrillist as one of the best new bars in America.

PanLex

PanLex is a linguistic project whose stated mission is to overcome language barriers to human rights, information, and opportunities. Started in 2004 at the University of Washington’s Turing Center, the project sought to build software that would enable all humans to use their native language to share information, ideas, and emotions with the rest of the world. This research produced a lexical database (TransGraph) designed to support panlingual translation, and a more powerful extension of it (PanDictionary) based on intelligent automated inference. After this work demonstrated the feasibility of the concept, the PanDictionary became the PanLex Database, and PanLex has continued to enlarge, enrich, and modify it by consulting multilingual dictionary and dictionary-like sources. In 2012, PanLex became a project of The Long Now Foundation.

In popular culture

Neal Stephenson's science fiction novel Anathem was partly inspired by the author's involvement with the Clock of the Long Now project. As a result of Brian Eno's work on the clock project, an album entitled January 07003 / Bell Studies for The Clock of The Long Now was released in 2003. English songwriter Owen Tromans released a single entitled "Long Now", inspired by the foundation, in 2013.

Board members

The Board of Directors of The Long Now Foundation as of February 2020:

Time formatting and storage bugs

From Wikipedia, the free encyclopedia
 
In computer science, time formatting and storage bugs are a class of software bugs which may cause time and date calculation or display to be improperly handled. These are most commonly manifestations of arithmetic overflow, but can also be the result of other issues. The most well-known consequence of bugs of this type is the Y2K problem, but many other milestone dates or times exist that have caused or will cause problems depending on various programming deficiencies.

Year 1970

During the 1960s, some computer programs were written using just a single digit for the year, so that 0–9 represented the years 1960–1969. It was especially easy to write programs in the COBOL language with this limitation. While many companies identified this problem in advance, some did not and outages occurred when the decade rolled over. The fix generally was to expand the year to just two digits, owing to limitations of the storage media common in that era, tab cards and magnetic tape.

Year 1975

On 4 January 1975, the 12-bit field that had been used for dates in the Decsystem 10 operating systems overflowed. There were numerous problems and crashes related to this bug while an alternative format was developed.

Year 1977

The PDP-8's OS/8 operating system used
  • 4 bits for the month
  • 5 bits for the date therein
  • 3 bits for the year.
This was recognized when COS-310 was developed, and dates were recorded differently.

Year 1989

Some mainframe programs were written to encode dates as the number of days since a 'zero date' of 1 January 1900, storing them as signed 16-bit binary integers. On 18 September 1989, these programs began to fail, the date being exactly 32,768 (215) days since the zero date. Values on and after this day do not fit into a signed 16-bit integer, but overflow and return negative values.

Year 1997

The Domain/OS clock, which is based on the number of 4-microsecond units that has occurred since 1 January 1980, rolled past 47 bits on 2 November 1997, rendering unpatched systems unusable.

Year 1999

In the last few months before the year 2000, two other date-related milestones occurred that received less publicity than the then-impending Y2K problem.

First GPS rollover

GPS dates are expressed as a week number and a day-of-week number, with the week number transmitted as a ten-bit value. This means that every 1024 weeks (about 19.6 years) after Sunday 6 January 1980 (the GPS epoch), the date resets again to that date; this happened for the first time at 23:59:47 on Saturday 21 August 1999, the second time at 23:59:42 UTC on 6 April 2019, and will happen again on 20 November 2038. To address this concern, modernised GPS navigation messages use a 13-bit field, which only repeats every 8,192 weeks (157 years), and will not return to zero until near the year 2137.

9/9/99

In many programs or data sets, "9/9/99" was used as a rogue value to indicate either an unresolved date or as a terminator to indicate no further data was in the set. This raised issues upon the arrival of the actual date this represents, 9 September 1999.

Year 2000

Two-digit year representations

Follow-on problems caused by certain temporary fixes to the Y2K problem will crop up at various points in the 21st century. Some programs were made Y2K-compliant by continuing to use two digit years, but picking an arbitrary year prior to which those years are interpreted as 20xx, and after which are interpreted as 19xx.

For example, a program may have been changed so that it treats two-digit year values 00–68 as referring to 2000 through 2068, and values 69–99 as referring to 1969 through 1999. Such a program will not be able to correctly deal with years beyond 2068.

For applications required to calculate the birth year (or another past year), such an algorithm has long been used to overcome the Year 1900 problem, but it has failed to recognise people over 100 years old.

Year 2010

Some systems had problems once the year rolled over to 2010. This was dubbed by some in the media as the "Y2K+10" or "Y2.01k" problem.

The main source of problems was confusion between hexadecimal number encoding and BCD encodings of numbers. The numbers 0 through 9 are encoded in both hexadecimal and BCD as 0016 through 0916. But the decimal number 10 is encoded in hexadecimal as 0A16 and in BCD as 1016. Thus a BCD 1016 interpreted as a hexadecimal encoding erroneously represents the decimal number 16.

For example, the SMS protocol uses BCD encoding for dates, so some mobile phone software incorrectly reported dates of messages as 2016 instead of 2010. Windows Mobile was the first software reported to have been affected by this glitch; in some cases WM6 changed the date of any incoming SMS message sent after 1 January 2010 from the year 2010 to 2016.

Other systems affected include EFTPOS terminals, and the PlayStation 3 (except the Slim model).

The most important such glitch occurred in Germany, where upwards of 20 million bank cards became unusable, and with Citibank Belgium, whose digipass customer identification chips stopped working.

Year 2011

Taiwan officially uses the Minguo calendar, which considers the Gregorian year 1912 to be its year 1. Thus, the Gregorian year 2011 is the ROC year 100, its first 3-digit year.

Year 2013

The unmanned Deep Impact spaceprobe lost communication with Earth on 11 August 2013, after a clock counted 232 deciseconds (tenths of seconds) since 1 January 2000.

Year 2019

Second GPS rollover

GPS dates are expressed as a week number and a day-of-week number, with the week number transmitted as a ten-bit value. This means that every 1024 weeks (about 19.6 years) after Sunday 6 January 1980 (the GPS epoch), the date resets again to that date; this happened for the first time at 23:59:47 on Saturday 21 August 1999, the second time at 23:59:42 UTC on 6 April 2019, and will happen again on 20 November 2038. To address this concern, modernised GPS navigation messages use a 13-bit field, which only repeats every 8,192 weeks (157 years), and will not return to zero until near the year 2137.

Japanese calendar transition

On 30 April 2019, Emperor Akihito of Japan abdicated favoring his son Naruhito. As years in Japan are traditionally referred to by era names that correspond to the reign of each emperor, this resulted in a new era name, Reiwa (令和), following Naruhito's accession to the throne the following day. Because the previous emperor, Hirohito, died in 1989 and Akihito's reign mostly corresponded with the rise in the use of computers, most software had not been tested to ensure correct behavior on an era change. Furthermore, testing was complicated by the fact that the new era name was not revealed until April 1, 2019. Therefore, errors were expected from software that did not anticipate a new era.

Classic Mac OS

The control panel in Classic Mac OS versions 6, 7, and 8 only allows the date to be set as high as December 31, 2019, although the system is able to continue to advance time beyond that date.

Year 2020

WWE 2K20 and Star Wars Jedi: Fallen Order would both crash on January 1, 2020, when the year rolled over. The glitches could only be circumvented by resetting the year back to 2019 until a patch was released. Additionally, Crystal Reports 8.5 would fail to generate specific reports starting in 2020.

Parkeon parking meters in New York City and other locations were unable to accept credit cards as a form of payment starting in 2020. A workaround was implemented, but required each meter to be individually updated. In New York, the meters were not expected to be fixed until January 9th.

In Poland, 5,000 cash registers stopped printing the date out properly.

SUUNTO sport smart watches showed out an error in computing week days, that was presented with a +2 step (aka: FRI rather WED, SAT rather than THU). For SUUNTO Spartan model watches, bug was fixed with firmware release 2.8.32.

Year 2028

During the late 1970s, on Data General Nova and Eclipse systems, World Computer Corporation (doing credit union applications) created this date format;
16-bit date field:
  • 128 years = 7 bits (1900+128=2028)
  • 12 months = 4 bits
  • 31 days = 5 bits
Dates were directly comparable using unsigned functions.
No known instances of this format are in use today.

Year 2031

Palm OS uses both signed integers with the 1970 epoch, as well as unsigned integers with the 1904 epoch, for different system functions, such as for system clock, and file dates (see PDB format). While this should result in Palm OS being susceptible to the 2038 problem, Palm OS also uses a 7-bit field for storing the year value, with a different epoch counting from 1904, resulting in a maximum year of (1904+127) 2031.

Year 2036

The Network Time Protocol has an overflow issue related to the Year 2038 problem, which manifests itself at 06:28:16 UTC on 7 February 2036, rather than 2038. The 64-bit timestamps used by NTP consist of a 32-bit part for seconds and a 32-bit part for fractional second, giving NTP a time scale that rolls over every 232 seconds (136 years) and a theoretical resolution of 2−32 second (233 picoseconds). NTP uses an epoch of 1 January 1900. The first rollover occurs in 2036, prior to the UNIX year 2038 problem.

Year 2038

Unix time rollover

The original implementation of the Unix operating system stored system time as a 32-bit signed integer representing the number of seconds past the Unix epoch: midnight UTC, 1 January 1970. This value will roll over on 19 January 2038. This problem has been addressed in most modern Unix and Unix-like operating systems by storing system time as a 64-bit signed integer, although individual applications, protocols, and file formats will still need to be changed as well.

DVB rollover

The Digital Video Broadcast system has an issue on 22 April 2038, when the 16 bits used to transmit Modified Julian Days used for electronic guide scheduling will restart from zero. The ETSI EN 300 368 specification mentions in Annex C that the provided MJD formulas are valid until 28 February 2100, but makes no mention of the limits imposed by the 16 bits used to transmit the resulting value.

Third GPS rollover

GPS dates are expressed as a week number and a day-of-week number, with the week number transmitted as a ten-bit value. This means that every 1024 weeks (about 19.6 years) after Sunday 6 January 1980 (the GPS epoch), the date resets again to that date; this happened for the first time at 23:59:47 on Saturday 21 August 1999, the second time at 23:59:42 UTC on 6 April 2019, and will happen again on 20 November 2038. To address this concern, modernised GPS navigation messages use a 13-bit field, which only repeats every 8,192 weeks (157 years), and will not return to zero until near the year 2137.

Year 2040

Early Apple Macintosh computers store time in their real-time clocks (RTCs) and HFS filesystems as an unsigned 32-bit number of seconds since 00:00:00 on 1 January 1904. After 06:28:15 on 6 February 2040, this will wrap around to 1904. HFS+, the default format for all of Apple's recent Macintosh computers, is also affected. The replacement Apple File System resolves this issue. 

ProDOS for the Apple II computers only supports two-digit year numbers. To avoid Y2K issues, Apple issued a technical note stating that the year number was to represent 1940-2039. Software for the platform may incorrectly display dates beginning in 2040. A third-party effort is underway to update ProDOS and application software to support years up to 2924.

Year 2042

On 18 September 2042, the Time of Day Clock (TODC) on the S/370 IBM mainframe and its successors, including the current zSeries, will roll over. The UTC time will be a few seconds earlier, due to leap seconds.

Older TODCs were implemented as a 64-bit count of 2−12 microsecond (0.244 ns) units, and the standard base was 1 January 1900 UT. In July 1999 the extended TODC clock was announced, which extended the clock to the right (that is, the extended bits are less significant than the original bits). The actual resolution depends on the model, but the format is consistent, and will, therefore, roll over after 252 microseconds.

The TODC value is accessible to user mode programs and is often used for timing and for generating unique IDs for events. 

While IBM has defined and implemented a longer (128-bit) hardware format on recent machines, which extends the timer on both ends by at least 8 additional bits, many programs continue to rely on the 64-bit format which remains as an accessible subset of the longer timer.

Year 2048

The ATSC system will have an issue similar to the DVB issue described above after 2048 due to its use of signed 32-bit GPS seconds that begin from 6 January 1980. 

The capacity planning logic in the ERP system SAP S/4HANA supports only finish dates up to 19 January 2048 (24855 days from 1 January 1980). This concerns e.g. the production, maintenance and inspection planning.

Year 2050

Various Texas Instruments calculators of the TI BA II Plus, TI BA II Plus Professional, TI-83, TI-84 and NSpire families support a function named dbd to calculate the number of days between dates. This function accepts dates between 1950-01-01 and 2049-12-31 only. One potential area where this will start causing problems in 2020 is in the calculation of 30-year mortgages.

Year 2079

Days 32,768 and 65,536

Programs that store dates as the number of days since an arbitrary date (or epoch) are vulnerable to roll-over or wrap-around effects if the values are not wide enough to allow the date values to span a large enough time range expected for the application. Signed 16-bit binary values roll over after 32,768 (215) days from the epoch date, producing negative values. Some mainframe systems experienced software failures because they had encoded dates as the number of days since 1 January 1900, which produced unexpected negative day numbers on the roll-over date of 18 September 1989. Similarly, unsigned 16-bit binary days counts overflow after 65,536 (216) days, which are truncated to zero values. For software using an epoch of 1 January 1900, this will occur on 6 June 2079.

Year 2080

Some (if not all) Nokia phones that run Series 40 (such as the Nokia X2-00) only supports dates up to 2079-12-31 and will refuse to change dates further than 2079-12-31. The workaround is to use the year 1996 in lieu of 2080 as a compatible leap year to display the correct day of the week, date and month on the main screen. 

Systems storing the year as a two-digit value 00..99 internally only (like many RTCs) may rollover from 2079-12-31 to the IBM PC and DOS epoch of 1980-01-01.

Year 2100

DOS and Windows file date API and conversion functions (such as INT 21h/AH=2Ah) officially support dates up to 2099-12-31 only (even though the underlying FAT filesystem would theoretically support dates up to 2107). Hence, DOS-based operating systems as well as applications that convert other formats to the FAT/DOS format, may show unexpected behavior starting 2100-01-01.

Another problem will emerge at the end of 2100-02-28, since 2100 is not a leap year, whereas many common implementations of the leap year algorithm are incomplete or simplified, and thus will erroneously assume it to be a leap year. This would cause the date to incorrectly roll over from 2100-02-28 to 2100-02-29, instead of directly to 2100-03-01.

Year 2106

Many existing file formats, communications protocols, and application interfaces employ a variant of the Unix time_t date format, storing the number of seconds since the Unix Epoch (midnight UTC, 1 January 1970) as an unsigned 32-bit binary integer. This value will roll over on 7 February 2106 at 06:28:15. That is, at this time the number of seconds since 01 January 1970 is FFFF FFFF in hex.

(This storage representation problem is independent of programs that internally store and operate on system times as 64-bit signed integer values.)

Year 2108

The date timestamps stored in FAT filesystems, originally introduced with 86-DOS 0.42 in 1981 and carried over into MS-DOS, PC DOS, DR-DOS etc., will overflow at the end of 2107-12-31. The last modification date stamp (and with DELWATCH 2.0+ also the file deletion date stamp, and since DOS 7.0+ optionally also the last access date stamp and creation date stamp), are stored in the directory entry with the year represented as an unsigned seven bit number (0–127), relative to 1980, and thereby unable to indicate any dates in the year 2108 and beyond. The API functions defined to retrieve these dates officially only support dates up to 2099-12-31. This will also affect the Zip archive file format, as it uses FAT file modification timestamps internally.

Year 2137

GPS dates are expressed as a week number and a day-of-week number, with the week number initially using a ten-bit value and modernised GPS navigation messages using a 13-bit field. Ten bit systems would rollover every 1024 weeks (about 19.6 years) after Sunday 6 January 1980 (the GPS epoch), and 13 bit systems rollover every 8192 weeks. 13 bit systems will rollover to zero in 2137.

Year 2262

The Go programming language has a UnixNano API that counts nanoseconds since 1970 as a 64-bit signed integer. This value will overflow on 2262-04-11. This is a limitation of similar nanosecond timekeeping systems, such as the Timestamp object in Python pandas, C++ chrono::system_clock or the QEMU timers.

Year 4501

Microsoft Outlook uses the date January 1, 4501 as a placeholder for "none" or "empty".

Year 10,000

The year 10,000 will be the first Gregorian year with five digits. Although many people at first consider this year to be so far distant that a problem of this type will never actually occur, certain classes of calculations in disciplines such as astronomy and physics already need to work with years of this magnitude and greater. These applications also have to deal with the Year zero problem. All future powers of 10 years have the potential for similar problems.

Year 30,828

Beginning 14 September 30,828, Windows will not accept dates beyond this day and on startup, Windows will complain about "invalid system time". This is because the FILETIME value in Windows, which is a 64-bit value corresponding to the number of 100-nanosecond intervals since 1 January 1601, 00:00:00.0000000 UTC, will overflow its maximum possible value on that day at 02:48:05.4775808 UTC.

Years 32,768 and 65,536

Programs that process years as 16-bit values may encounter problems dealing with either the year 32,768 or 65,536, depending on whether the value is treated as a signed or unsigned integer.

For the year 32,768 problem, years after 32,767 may be interpreted as negative numbers, beginning with −32,768. The year 65,536 problem is more likely to manifest itself by representing the year 65,536 as the year 0.

Relative time overflow

Microsoft

In Microsoft Windows 7, Windows Server 2003, Windows Server 2008 and Windows Vista, TCP connection start information was stored in 1/100ths of a second, using a 32bit unsigned integer, causing an overflow and TCP connections to fail after 497 days.

Boeing

The Boeing 787 aircraft has had at least two software issues related to time storage. In 2015 an error was reported where time was stored in 1/100ths of a second, using a signed 32-bit integer, and the systems would crash after 248 days. In 2020, the FAA issued an airworthiness directive for a problem where, if the aircraft is not powered down completely before reaching 51 days of uptime, systems will begin to display misleading data.

Far-fetched problems

Certain problematic years occur so far in the future, well beyond the likely lifespan of the Earth, the Sun, humanity, and even past some predictions of the lifetime of the universe, that they are mainly referenced as matters of theoretical interest, jokes, or indications that a related problem is not truly solved for any reasonable definition of “solved”.
  • The year 292,277,026,596 (2.9×1011) and 584,554,051,223 (5.8×1011) problems: the years that 64-bit Unix time becomes negative (assuming a signed number) or reset to zero (for an unsigned representation). The year 5,391,559,471,918,239,497,011,222,876,596 (5.4×1030) and 10,783,118,943,836,478,994,022,445,751,223 (1.1×1031) problems: the years that 128-bit Unix time becomes negative (assuming a signed number) or reset to zero (for an unsigned representation).
Note: these year values are based on an average year of exactly 365.2425 days, which matches the 4/100/400 leap year rules of the commonly used Gregorian calendar. Additional adjustments to the calendar over intervals this long are unavoidable, as the actual year is currently slightly shorter (about 365.242374 days) than assumed, the length of Earth's orbit around the Sun changes over time (tropical years are currently becoming shorter at about 0.53 seconds per century), and in any case, all of these times far exceed the likely existence of the Earth. So the year numbers should be considered approximate.

Time zone and daylight saving time

Time zones and daylight saving time can cause trouble in computer applications when:
  • Communicating between places with different time zones or using the same device in a different time zone
  • Daylight saving time starts and ends, especially in the fall when the same time occurs twice
  • The time zone in a specific area changes or daylight saving time is adjusted, especially when there isn't enough time for software and firmware to be updated accordingly
  • The time shifts less or more than 1 hour forward in the spring
  • The start/end dates of summer time depend on other astronomical events
  • Daylight saving time is not adopted by everyone in the same place

Equality (mathematics)

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Equality_...