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Friday, November 17, 2023

Software bug

From Wikipedia, the free encyclopedia

Bugs in software can arise from mistakes and errors made in interpreting and extracting users' requirements, planning a program's design, writing its source code, and from interaction with humans, hardware and programs, such as operating systems or libraries. A program with many, or serious, bugs is often described as buggy. Bugs can trigger errors that may have ripple effects. The effects of bugs may be subtle, such as unintended text formatting, through to more obvious effects such as causing a program to crash, freezing the computer, or causing damage to hardware. Other bugs qualify as security bugs and might, for example, enable a malicious user to bypass access controls in order to obtain unauthorized privileges.

Some software bugs have been linked to disasters. Bugs in code that controlled the Therac-25 radiation therapy machine were directly responsible for patient deaths in the 1980s. In 1996, the European Space Agency's US$1 billion prototype Ariane 5 rocket was destroyed less than a minute after launch due to a bug in the on-board guidance computer program. In 1994, an RAF Chinook helicopter crashed, killing 29; this was initially blamed on pilot error, but was later thought to have been caused by a software bug in the engine-control computer. Buggy software caused the early 21st century British Post Office scandal, the most widespread miscarriage of justice in British legal history.

In 2002, a study commissioned by the US Department of Commerce's National Institute of Standards and Technology concluded that "software bugs, or errors, are so prevalent and so detrimental that they cost the US economy an estimated $59 billion annually, or about 0.6 percent of the gross domestic product".

History

The Middle English word bugge is the basis for the terms "bugbear" and "bugaboo" as terms used for a monster.

The term "bug" to describe defects has been a part of engineering jargon since the 1870s and predates electronics and computers; it may have originally been used in hardware engineering to describe mechanical malfunctions. For instance, Thomas Edison wrote in a letter to an associate in 1878:

... difficulties arise—this thing gives out and [it is] then that "Bugs"—as such little faults and difficulties are called—show themselves

Baffle Ball, the first mechanical pinball game, was advertised as being "free of bugs" in 1931. Problems with military gear during World War II were referred to as bugs (or glitches). In a book published in 1942, Louise Dickinson Rich, speaking of a powered ice cutting machine, said, "Ice sawing was suspended until the creator could be brought in to take the bugs out of his darling."

Isaac Asimov used the term "bug" to relate to issues with a robot in his short story "Catch That Rabbit", published in 1944.

The term "bug" was used in an account by computer pioneer Grace Hopper, who publicized the cause of a malfunction in an early electromechanical computer. A typical version of the story is:

In 1946, when Hopper was released from active duty, she joined the Harvard Faculty at the Computation Laboratory where she continued her work on the Mark II and Mark III. Operators traced an error in the Mark II to a moth trapped in a relay, coining the term bug. This bug was carefully removed and taped to the log book. Stemming from the first bug, today we call errors or glitches in a program a bug.

Hopper was not present when the bug was found, but it became one of her favorite stories. The date in the log book was September 9, 1947. The operators who found it, including William "Bill" Burke, later of the Naval Weapons Laboratory, Dahlgren, Virginia, were familiar with the engineering term and amusedly kept the insect with the notation "First actual case of bug being found." This log book, complete with attached moth, is part of the collection of the Smithsonian National Museum of American History.

The related term "debug" also appears to predate its usage in computing: the Oxford English Dictionary's etymology of the word contains an attestation from 1945, in the context of aircraft engines.

The concept that software might contain errors dates back to Ada Lovelace's 1843 notes on the analytical engine, in which she speaks of the possibility of program "cards" for Charles Babbage's analytical engine being erroneous:

... an analysing process must equally have been performed in order to furnish the Analytical Engine with the necessary operative data; and that herein may also lie a possible source of error. Granted that the actual mechanism is unerring in its processes, the cards may give it wrong orders.

Terminology

While the use of the term "bug" to describe software errors is common, many have suggested that it should be abandoned. One argument is that the word "bug" is divorced from a sense that a human being caused the problem, and instead implies that the defect arose on its own, leading to a push to abandon the term "bug" in favor of terms such as "defect", with limited success.

The term "bug" may also be used to cover up an intentional design decision. In 2011, after receiving scrutiny from US Senator Al Franken for recording and storing users' locations in unencrypted files, Apple called the behavior a bug. However, Justin Brookman of the Center for Democracy and Technology directly challenged that portrayal, stating "I'm glad that they are fixing what they call bugs, but I take exception with their strong denial that they track users."

In software engineering, mistake metamorphism (from Greek meta = "change", morph = "form") refers to the evolution of a defect in the final stage of software deployment. Transformation of a "mistake" committed by an analyst in the early stages of the software development lifecycle, which leads to a "defect" in the final stage of the cycle has been called 'mistake metamorphism'.

Different stages of a "mistake" in the entire cycle may be described as "mistakes", "anomalies", "faults", "failures", "errors", "exceptions", "crashes", "glitches", "bugs", "defects", "incidents", or "side effects".

Prevention

The software industry has put much effort into reducing bug counts. These include:

Typographical errors

Bugs usually appear when the programmer makes a logic error. Various innovations in programming style and defensive programming are designed to make these bugs less likely, or easier to spot. Some typos, especially of symbols or operators, allow the program to operate incorrectly, while others such as a missing symbol or misspelled name may prevent the program from operating. Compiled languages can reveal some typos when the source code is compiled.

Development methodologies

Several schemes assist managing programmer activity so that fewer bugs are produced. Software engineering (which addresses software design issues as well) applies many techniques to prevent defects. For example, formal program specifications state the exact behavior of programs so that design bugs may be eliminated. Formal specifications are impractical for anything but the shortest programs, because of problems of combinatorial explosion and indeterminacy.

Unit testing involves writing a test for every function (unit) that a program is to perform.

In test-driven development unit tests are written before the code and the code is not considered complete until all tests complete successfully.

Agile software development involves frequent software releases with relatively small changes. Defects are revealed by user feedback.

Open source development allows anyone to examine source code. A school of thought popularized by Eric S. Raymond as Linus's law says that popular open-source software has more chance of having few or no bugs than other software, because "given enough eyeballs, all bugs are shallow". This assertion has been disputed, however: computer security specialist Elias Levy wrote that "it is easy to hide vulnerabilities in complex, little understood and undocumented source code," because, "even if people are reviewing the code, that doesn't mean they're qualified to do so." An example of an open-source software bug was the 2008 OpenSSL vulnerability in Debian.

Programming language support

Programming languages include features to help prevent bugs, such as static type systems, restricted namespaces and modular programming. For example, when a programmer writes (pseudocode) LET REAL_VALUE PI = "THREE AND A BIT", although this may be syntactically correct, the code fails a type check. Compiled languages catch this without having to run the program. Interpreted languages catch such errors at runtime. Some languages deliberately exclude features that easily lead to bugs, at the expense of slower performance: the general principle being that, it is almost always better to write simpler, slower code than inscrutable code that runs slightly faster, especially considering that maintenance cost is substantial. For example, the Java programming language does not support pointer arithmetic; implementations of some languages such as Pascal and scripting languages often have runtime bounds checking of arrays, at least in a debugging build.

Code analysis

Tools for code analysis help developers by inspecting the program text beyond the compiler's capabilities to spot potential problems. Although in general the problem of finding all programming errors given a specification is not solvable (see halting problem), these tools exploit the fact that human programmers tend to make certain kinds of simple mistakes often when writing software.

Instrumentation

Tools to monitor the performance of the software as it is running, either specifically to find problems such as bottlenecks or to give assurance as to correct working, may be embedded in the code explicitly (perhaps as simple as a statement saying PRINT "I AM HERE"), or provided as tools. It is often a surprise to find where most of the time is taken by a piece of code, and this removal of assumptions might cause the code to be rewritten.

Testing

Software testers are people whose primary task is to find bugs, or write code to support testing. On some efforts, more resources may be spent on testing than in developing the program.

Measurements during testing can provide an estimate of the number of likely bugs remaining; this becomes more reliable the longer a product is tested and developed.

Debugging

Finding and fixing bugs, or debugging, is a major part of computer programming. Maurice Wilkes, an early computing pioneer, described his realization in the late 1940s that much of the rest of his life would be spent finding mistakes in his own programs.

Usually, the most difficult part of debugging is finding the bug. Once it is found, correcting it is usually relatively easy. Programs known as debuggers help programmers locate bugs by executing code line by line, watching variable values, and other features to observe program behavior. Without a debugger, code may be added so that messages or values may be written to a console or to a window or log file to trace program execution or show values.

However, even with the aid of a debugger, locating bugs is something of an art. It is not uncommon for a bug in one section of a program to cause failures in a completely different section, thus making it especially difficult to track (for example, an error in a graphics rendering routine causing a file I/O routine to fail), in an apparently unrelated part of the system.

Sometimes, a bug is not an isolated flaw, but represents an error of thinking or planning on the part of the programmer. Such logic errors require a section of the program to be overhauled or rewritten. As a part of code review, stepping through the code and imagining or transcribing the execution process may often find errors without ever reproducing the bug as such.

More typically, the first step in locating a bug is to reproduce it reliably. Once the bug is reproducible, the programmer may use a debugger or other tool while reproducing the error to find the point at which the program went astray.

Some bugs are revealed by inputs that may be difficult for the programmer to re-create. One cause of the Therac-25 radiation machine deaths was a bug (specifically, a race condition) that occurred only when the machine operator very rapidly entered a treatment plan; it took days of practice to become able to do this, so the bug did not manifest in testing or when the manufacturer attempted to duplicate it. Other bugs may stop occurring whenever the setup is augmented to help find the bug, such as running the program with a debugger; these are called heisenbugs (humorously named after the Heisenberg uncertainty principle).

Since the 1990s, particularly following the Ariane 5 Flight 501 disaster, interest in automated aids to debugging rose, such as static code analysis by abstract interpretation.

Some classes of bugs have nothing to do with the code. Faulty documentation or hardware may lead to problems in system use, even though the code matches the documentation. In some cases, changes to the code eliminate the problem even though the code then no longer matches the documentation. Embedded systems frequently work around hardware bugs, since to make a new version of a ROM is much cheaper than remanufacturing the hardware, especially if they are commodity items.

Benchmark of bugs

To facilitate reproducible research on testing and debugging, researchers use curated benchmarks of bugs:

the Siemens benchmark
ManyBugs is a benchmark of 185 C bugs in nine open-source programs.
Defects4J is a benchmark of 341 Java bugs from 5 open-source projects. It contains the corresponding patches, which cover a variety of patch type.

Bug management

Bug management includes the process of documenting, categorizing, assigning, reproducing, correcting and releasing the corrected code. Proposed changes to software – bugs as well as enhancement requests and even entire releases – are commonly tracked and managed using bug tracking systems or issue tracking systems. The items added may be called defects, tickets, issues, or, following the agile development paradigm, stories and epics. Categories may be objective, subjective or a combination, such as version number, area of the software, severity and priority, as well as what type of issue it is, such as a feature request or a bug.

A bug triage reviews bugs and decides whether and when to fix them. The decision is based on the bug's priority, and factors such as development schedules. The triage is not meant to investigate the cause of bugs, but rather the cost of fixing them. The triage happens regularly, and goes through bugs opened or reopened since the previous meeting. The attendees of the triage process typically are the project manager, development manager, test manager, build manager, and technical experts.

Severity

Severity is the intensity of the impact the bug has on system operation. This impact may be data loss, financial, loss of goodwill and wasted effort. Severity levels are not standardized. Impacts differ across industry. A crash in a video game has a totally different impact than a crash in a web browser, or real time monitoring system. For example, bug severity levels might be "crash or hang", "no workaround" (meaning there is no way the customer can accomplish a given task), "has workaround" (meaning the user can still accomplish the task), "visual defect" (for example, a missing image or displaced button or form element), or "documentation error". Some software publishers use more qualified severities such as "critical", "high", "low", "blocker" or "trivial". The severity of a bug may be a separate category to its priority for fixing, and the two may be quantified and managed separately.

Priority

Priority controls where a bug falls on the list of planned changes. The priority is decided by each software producer. Priorities may be numerical, such as 1 through 5, or named, such as "critical", "high", "low", or "deferred". These rating scales may be similar or even identical to severity ratings, but are evaluated as a combination of the bug's severity with its estimated effort to fix; a bug with low severity but easy to fix may get a higher priority than a bug with moderate severity that requires excessive effort to fix. Priority ratings may be aligned with product releases, such as "critical" priority indicating all the bugs that must be fixed before the next software release.

A bug severe enough to delay or halt the release of the product is called a "show stopper" or "showstopper bug". It is named so because it "stops the show" – causes unacceptable product failure.

Software releases

It is common practice to release software with known, low-priority bugs. Bugs of sufficiently high priority may warrant a special release of part of the code containing only modules with those fixes. These are known as patches. Most releases include a mixture of behavior changes and multiple bug fixes. Releases that emphasize bug fixes are known as maintenance releases, to differentiate it from major releases that emphasize feature additions or changes.

Reasons that a software publisher opts not to patch or even fix a particular bug include:

A deadline must be met and resources are insufficient to fix all bugs by the deadline.
The bug is already fixed in an upcoming release, and it is not of high priority.
The changes required to fix the bug are too costly or affect too many other components, requiring a major testing activity.
It may be suspected, or known, that some users are relying on the existing buggy behavior; a proposed fix may introduce a breaking change.
The problem is in an area that will be obsolete with an upcoming release; fixing it is unnecessary.
"It's not a bug, it's a feature". A misunderstanding has arisen between expected and perceived behavior or undocumented feature.

Types

In software development, a mistake or error may be introduced at any stage. Bugs arise from oversight or misunderstanding by a software team during specification, design, coding, configuration, data entry or documentation. For example, a relatively simple program to alphabetize a list of words, the design might fail to consider what should happen when a word contains a hyphen. Or when converting an abstract design into code, the coder might inadvertently create an off-by-one error which can be a "<" where "<=" was intended, and fail to sort the last word in a list.

Another category of bug is called a race condition that may occur when programs have multiple components executing at the same time. If the components interact in a different order than the developer intended, they could interfere with each other and stop the program from completing its tasks. These bugs may be difficult to detect or anticipate, since they may not occur during every execution of a program.

Conceptual errors are a developer's misunderstanding of what the software must do. The resulting software may perform according to the developer's understanding, but not what is really needed. Other types:

Arithmetic

In operations on numerical values, problems can arise that result in unexpected output, slowing of a process, or crashing. These can be from a lack of awareness of the qualities of the data storage such as a loss of precision due to rounding, numerically unstable algorithms, arithmetic overflow and underflow, or from lack of awareness of how calculations are handled by different software coding languages such as division by zero which in some languages may throw an exception, and in others may return a special value such as NaN or infinity.

Control flow

Control flow bugs are those found in processes with valid logic, but that lead to unintended results, such as infinite loops and infinite recursion, incorrect comparisons for conditional statements such as using the incorrect comparison operator, and off-by-one errors (counting one too many or one too few iterations when looping).

Interfacing

Incorrect API usage.
Incorrect protocol implementation.
Incorrect hardware handling.
Incorrect assumptions of a particular platform.
Incompatible systems. A new API or communications protocol may seem to work when two systems use different versions, but errors may occur when a function or feature implemented in one version is changed or missing in another. In production systems which must run continually, shutting down the entire system for a major update may not be possible, such as in the telecommunication industry or the internet. In this case, smaller segments of a large system are upgraded individually, to minimize disruption to a large network. However, some sections could be overlooked and not upgraded, and cause compatibility errors which may be difficult to find and repair.
Incorrect code annotations.

Concurrency

Deadlock, where task A cannot continue until task B finishes, but at the same time, task B cannot continue until task A finishes.
Race condition, where the computer does not perform tasks in the order the programmer intended.
Concurrency errors in critical sections, mutual exclusions and other features of concurrent processing. Time-of-check-to-time-of-use (TOCTOU) is a form of unprotected critical section.

Resourcing

Null pointer dereference.
Using an uninitialized variable.
Using an otherwise valid instruction on the wrong data type (see packed decimal/binary-coded decimal).
Access violations.
Resource leaks, where a finite system resource (such as memory or file handles) become exhausted by repeated allocation without release.
Buffer overflow, in which a program tries to store data past the end of allocated storage. This may or may not lead to an access violation or storage violation. These are frequently security bugs.
Excessive recursion which—though logically valid—causes stack overflow.
Use-after-free error, where a pointer is used after the system has freed the memory it references.
Double free error.

Syntax

Use of the wrong token, such as performing assignment instead of equality test. For example, in some languages x=5 will set the value of x to 5 while x==5 will check whether x is currently 5 or some other number. Interpreted languages allow such code to fail. Compiled languages can catch such errors before testing begins.

Teamwork

Unpropagated updates; e.g. programmer changes "myAdd" but forgets to change "mySubtract", which uses the same algorithm. These errors are mitigated by the Don't Repeat Yourself philosophy.
Comments out of date or incorrect: many programmers assume the comments accurately describe the code.
Differences between documentation and product.

Implications

The amount and type of damage a software bug may cause naturally affects decision-making, processes and policy regarding software quality. In applications such as human spaceflight, aviation, nuclear power, health care, public transport or automotive safety, since software flaws have the potential to cause human injury or even death, such software will have far more scrutiny and quality control than, for example, an online shopping website. In applications such as banking, where software flaws have the potential to cause serious financial damage to a bank or its customers, quality control is also more important than, say, a photo editing application.

Other than the damage caused by bugs, some of their cost is due to the effort invested in fixing them. In 1978, Lientz et al. showed that the median of projects invest 17 percent of the development effort in bug fixing. In 2020, research on GitHub repositories showed the median is 20%.

Residual bugs in delivered product

In 1994, NASA's Goddard Space Flight Center managed to reduce their average number of errors from 4.5 per 1000 lines of code (SLOC) down to 1 per 1000 SLOC.

Another study in 1990 reported that exceptionally good software development processes can achieve deployment failure rates as low as 0.1 per 1000 SLOC. This figure is iterated in literature such as Code Complete by Steve McConnell, and the NASA study on Flight Software Complexity. Some projects even attained zero defects: the firmware in the IBM Wheelwriter typewriter which consists of 63,000 SLOC, and the Space Shuttle software with 500,000 SLOC.

Well-known bugs

A number of software bugs have become well-known, usually due to their severity: examples include various space and military aircraft crashes. Possibly the most famous bug is the Year 2000 problem or Y2K bug, which caused many programs written long before the transition from 19xx to 20xx dates to malfunction, for example treating a date such as "25 Dec 04" as being in 1904, displaying "19100" instead of "2000", and so on. A huge effort at the end of the 20th century resolved the most severe problems, and there were no major consequences.

The 2012 stock trading disruption involved one such incompatibility between the old API and a new API.

In politics

"Bugs in the System" report

The Open Technology Institute, run by the group, New America, released a report "Bugs in the System" in August 2016 stating that U.S. policymakers should make reforms to help researchers identify and address software bugs. The report "highlights the need for reform in the field of software vulnerability discovery and disclosure." One of the report's authors said that Congress has not done enough to address cyber software vulnerability, even though Congress has passed a number of bills to combat the larger issue of cyber security.

Government researchers, companies, and cyber security experts are the people who typically discover software flaws. The report calls for reforming computer crime and copyright laws.

The Computer Fraud and Abuse Act, the Digital Millennium Copyright Act and the Electronic Communications Privacy Act criminalize and create civil penalties for actions that security researchers routinely engage in while conducting legitimate security research, the report said.

In popular culture

In video gaming, the term "glitch" is sometimes used to refer to a software bug. An example is the glitch and unofficial Pokémon species MissingNo.
In both the 1968 novel 2001: A Space Odyssey and the corresponding 1968 film 2001: A Space Odyssey, a spaceship's onboard computer, HAL 9000, attempts to kill all its crew members. In the follow-up 1982 novel, 2010: Odyssey Two, and the accompanying 1984 film, 2010, it is revealed that this action was caused by the computer having been programmed with two conflicting objectives: to fully disclose all its information, and to keep the true purpose of the flight secret from the crew; this conflict caused HAL to become paranoid and eventually homicidal.
In the English version of the Nena 1983 song 99 Luftballons (99 Red Balloons) as a result of "bugs in the software", a release of a group of 99 red balloons are mistaken for an enemy nuclear missile launch, requiring an equivalent launch response, resulting in catastrophe.
In the 1999 American comedy Office Space, three employees attempt (unsuccessfully) to exploit their company's preoccupation with the Y2K computer bug using a computer virus that sends rounded-off fractions of a penny to their bank account—a long-known technique described as salami slicing.
The 2004 novel The Bug, by Ellen Ullman, is about a programmer's attempt to find an elusive bug in a database application.
The 2008 Canadian film Control Alt Delete is about a computer programmer at the end of 1999 struggling to fix bugs at his company related to the year 2000 problem.

Time formatting and storage bugs

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

In computer science, time formatting and storage bugs are a class of software bugs that cause errors in time and date calculation or display. 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 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 1978

The Digital Equipment Corporation OS/8 operating system for the PDP-8 computer used only three bits for the year, representing the years 1970 to 1977.

This was recognized when the COS-310 operating system was developed, and dates were recorded differently.

Year 1993

Multiple Sierra Entertainment games released for the Classic Mac OS started to freeze when running on 18 September 1993. An issue in the Mac version of Sierra's Creative Interpreter (Mac SCI) would cause the game to "lock-up" when attempting to handle a delay due to a problem involving an overflow. Mac SCI would attempt to use the date to determine how long a delay should last by getting the current time in seconds since 1 January 1904, the Macintosh epoch, and dividing by 12 hours. The division was processed by the Motorola 68000 and would not occur if an overflow was detected because of the division, but the Mac SCI would continue on regardless as if the division had occurred, eventually resulting in a delay of one second being treated as a delay for 18 hours and so on. Sierra released a patch called MCDATE that resolved the problem for almost 14 years.

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 1,024 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 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 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 2001

Systems that used a string of nine digits to record the time as seconds since the Unix epoch had issues reporting times beyond the one-billionth second after the epoch on 9 September 2001 at 01:46:40 (the "billenium"). Problems were not widespread.

Year 2007

Sierra Entertainment games for the Classic Mac OS that were patched with the MCDATE program or released afterwards with the patch built in would begin to freeze on 28 May 2007. As with the Year 1993 program, this was due to an issue in the Mac SCI when attempting to use the date to determine how long a delay should last. Programs with the MCDATE patch freeze because the Mac SCI takes the current number of seconds since the Macintosh epoch of 1 January 1904, subtracts 432,000,000 seconds from that, and then divides by 12 hours through the Motorola 68000, to then determine how long delays should last. On 28 May 2007, the Motorola 68000 again does not divide due to overflow protection, which the Mac SCI ignores.

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).

Sony's PlayStation 3 incorrectly treated 2010 as a leap year, so the non-existent 29 February 2010, was shown on 1 March 2010, causing a program error.

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 Deep Impact space probe lost communication with Earth on 11 August 2013, because of a time-tagging problem; the date was stored as an unsigned 32-bit integer counting the number of tenth-seconds since 1 January 2000.

Year 2019

Second GPS rollover

In 2019, the second GPS week number rollover occurred.

Japanese calendar transition

On 30 April 2019, Emperor Akihito of Japan abdicated in favor of 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 7 January 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, while testing was further complicated by the fact that the new era name was not revealed until 1 April 2019. Therefore, errors were expected from software that did not anticipate a new era.

Year 2020

The video games WWE 2K20 and Star Wars Jedi: Fallen Order both crashed on 1 January 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 9 January.

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

Suunto sport smart watches displayed an error in computing weekdays that were presented with a +2 step (e.g. FRI rather than WED, SAT rather than THU). For Suunto Spartan model watches, the bug was fixed with firmware release 2.8.32.

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 31 December 2019, although the system is able to continue to advance time beyond that date.

Year 2021

Samsung users reported that phones running on the latest One UI 3.0 update or Android 11 lost access to the battery and charging statistics starting in 2021. Affected devices would not report usage statistics, thus leaving those sections blank.

Year 2022

Dates that are stored in the format yymmddHHMM converted to a signed 32-bit integer overflowed on 1 January 2022, as 2³¹=2147483648. Notably affected was the malware-scanning component update numbers of Microsoft Exchange, which appear to be used for a mathematical check to determine the latest update.

Honda and Acura cars manufactured between 2004 and 2012 containing GPS navigation systems incorrectly displayed the year as 2002. This problem was due to an overflow on the GPS epoch. The issue was resolved on August 17, 2022.

Year 2025

In Japan, some older computer systems using the Japanese calendar that have not been updated still count years according to the Shōwa era. The year 2025 corresponds in those systems to Shōwa 100, which can cause problems if the software assumes two digits for the year.

Year 2028

Some systems store their year as a single-byte offset from 1900, which gives a range of 255 (8 bits) and allows dates up to 2155 to be safely represented. However, not all systems use an unsigned byte: some have been mistakenly coded with a signed byte which only allows a range of 127 years, meaning that the date field in the software will be incorrect after 2027 and can cause unpredictable behaviour. Several pieces of optical-disc software that operate using the ISO 9660 format are affected by this.

During the late 1970s, on Data General Nova and Eclipse systems, the World Computer Corporation (doing credit union applications) created a date format with a 16-bit date field for 128 years (7 bits – note 1900+128=2028), 12 months (4 bits) and 31 days (5 bits). This allowed dates to be directly comparable using unsigned functions. Some systems, including HP 3000, still use this format, although a patch has been developed by outside consultants.

Year 2032

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 2031 (1904+127).

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 00:00:00 on Thursday, 1 January 1970. This value will roll over after 03:14:07 UTC on Tuesday, 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 must be changed as well.

Windows C runtime library

Like the Unix time rollover issue, the 32-bit version of gmtime in the C runtime libraries on Windows has a similar problem.

This problem has already manifested in Oracle's Access Manager version 10.1.4.3 for Windows. The Identity Console component sets a cookie containing UI preferences with an expiry of 500,000,000 seconds in the future (15 years, 308 days, 53 minutes and 20 seconds). This is beyond 19 January 2038 and so it throws an exception for certain search activities after 17 March 2022, at 02:20:48 because the gmtime_r() call cannot convert the number provided to a date to write to the cookie. Despite the age of the software (18 June 2009), Oracle issued a patch number 33983548 on 6 April 2022.

Third GPS rollover

The third GPS week number rollover will occur at 20 November 2038, at 23:59:37 UTC.

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, (i.e. 2³²−1 seconds from the epoch), this will wrap around to 1904: further to this, 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, though a third-party effort is underway to update ProDOS and application software to support years up to 4095.

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.

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, (24,855 days from 1 January 1980). This concerns e.g. the production, maintenance and inspection planning.

Year 2069

According to the Single UNIX Specification for parsing two-digit years using strptime(), "values in the range [69,99] shall refer to years 1969 to 1999 inclusive and values in the range [00,68] shall refer to years 2000 to 2068 inclusive", meaning that, when parsed by strptime(), the two-digit year "69" would be interpreted as 1969 rather than 2069.

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 support dates up to 31 December 2079, and thus will be unable to display dates after this. One workaround is to use the year 1996, 2024 or 2052 in lieu of 2080 (as compatible leap years) 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 roll over from 31 December 2079, 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 31 December 2099, 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 1 January 2100.

Another problem will emerge at the end of 28 February 2100, since 2100 is not a leap year. As many common implementations of the leap year algorithm are incomplete or are simplified, they may erroneously assume 2100 to be a leap year, causing the date to roll over from 28 February 2100 to 29 February 2100, instead of 1 March 2100.

The Nintendo DS and GameCube, as well as the Sony PlayStation 4, only allow users to set dates up to the year 2099. In the case of the Nintendo DS, the system will not advance time beyond 31 December 2099, whereas the GameCube and PS4 will still roll over into 2100 and beyond, even though users of those game consoles cannot manually input the date and time that far out.

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 1 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 25 February 1981 and carried over into MS-DOS, PC DOS, DR-DOS etc., will overflow at the end of 31 December 2107. 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 31 December 2099.

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 roll over every 1024 weeks (about 19.6 years) after Sunday 6 January 1980 (the GPS epoch), and 13-bit systems roll over every 8192 weeks. Thirteen-bit systems will roll over to zero in 2137.

Year 2248

RISC OS stores dates as centiseconds since the start of Monday 1st January 1900 in five bytes – 40 bits. These timestamps are used internally and exposed in file metadata (load and exec addresses). This epoch ends on 3rd June 2248 at 06:57:57.75 UTC.

Year 2262

Some timekeeping systems count nanoseconds since 1970 using a 64-bit signed integer, which will overflow at 11 April 2262, 23:47:16. The Go programming language's UnixNano API is one example. Other examples include the Timestamp object in Python pandas, C++ chrono::system_clock, and the QEMU timers.

Year 2286

Systems that use a string of length 10 characters to record the Unix time may have problems reporting times beyond the ten-billionth second after 20 November 2286, at 17:46:40.

Years 4000, 8000, etc.

On time scales of thousands of years, the Gregorian calendar falls behind the astronomical seasons. This is because the Earth's speed of rotation is gradually slowing down, which makes each day slightly longer over time (see tidal acceleration and leap second) while the year maintains a more uniform duration.

In the 19th century, Sir John Herschel proposed a modification to the Gregorian calendar with 969 leap days every 4000 years, instead of 970 leap days that the Gregorian calendar would insert over the same period. This would reduce the average year to 365.24225 days. Herschel's proposal would make the year 4000, and multiples thereof, common instead of leap. While this modification has often been proposed since, it has never been officially adopted.

While most software (including Excel, JavaScript and R) currently recognizes 4000 and 8000 as leap years (as they are divisible by 400), SAS has adopted the "4000 year rule". Thus, with the current software, date conversions between SAS and other software will go out of sync after 28 February 4000.

Year 4501

Microsoft Outlook uses the date 1 January 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, there is a tendency for programs and computer code to be recycled well past the lifetime of their original software or hardware. All future years that are powers of 10, as well as dates before the 10th millennium BC, face similar encoding problems.

Examples

This problem can be seen in the spreadsheet program Microsoft Excel as of 2023, which stores dates as the number of days since 31 December 1899 (day 1 is 1 January 1900) with a fictional leap day in 1900 if using the default 1900 date system. Alternatively, if using the 1904 date system, the date is stored as the number of days since 1 January 1904 (day 1 is 2 January 1904), and there is no leap year problem. The maximum supported date for calculation is 31 December 9999.

Year 30,828

Beginning 14 September 30,828, Windows will not accept dates beyond this day and on startup, it will display an error regarding "invalid system time" in NTFS. 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.

Year 100,000

The year 100,000 will be the first Gregorian year with six digits.

Year 275,760

JavaScript's Date API stores dates as the number of milliseconds since 1 January 1970. Dates have a range of ±100,000,000 days from the epoch, meaning that programs written in JavaScript using the Date API cannot store dates past 13 September, AD 275,760.

Year 292,277,026,596

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 problem (about 2.9×10¹¹ years in the future) will occur when the 64-bit Unix time overflows after UTC 15:30:08 on Sunday, 4 December, AD 292,277,026,596.

Relative time overflow

Microsoft

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

Microsoft Windows 95 and Windows 98 had a problem with 2^32 millisecond rollover in a virtual device driver (VTDAPI.VXD), which caused systems to hang after 49.7 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 hundredths 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.

Arduino

The Arduino platform provides a relative time via the millis() function. This function returns an unsigned 32 bit value for "milliseconds since startup", which is designed to roll over every 49.71 days. By default, this is the only timing source available in the platform and programs need to take special care to handle rollovers. Internally, millis() is based on counting timer interrupts. Certain powersave modes disable interrupts and therefore stop the counter from advancing during sleep.

Historic year problems

Also for historic years there might be problems when handling historic events, for example:

Year 2038 problem

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Year_2038_problem

An animated visual of the bug in action. The overflow error will occur at 03:14:08 UTC on 19 January 2038.

The year 2038 problem (also known as Y2038, Y2K38, Y2K38 superbug or the Epochalypse) is a time formatting bug in computer systems with representing times after 03:14:07 UTC on 19 January 2038.

The problem exists in systems which measure Unix time – the number of seconds elapsed since the Unix epoch (00:00:00 UTC on 1 January 1970) – and store it in a signed 32-bit integer. The data type is only capable of representing integers between −(2³¹) and 2³¹ − 1, meaning the latest time that can be properly encoded is 2³¹ − 1 seconds after epoch (03:14:07 UTC on 19 January 2038). Attempting to increment to the following second (03:14:08) will cause the integer to overflow, setting its value to −(2³¹) which systems will interpret as 2³¹ seconds before epoch (20:45:52 UTC on 13 December 1901). The problem is similar in nature to the year 2000 problem.

Computer systems that use time for critical computations may encounter fatal errors if the Y2038 problem is not addressed. Some applications that use future dates have already encountered the bug. The most vulnerable systems are those which are infrequently or never updated, such as legacy and embedded systems. There is no universal solution to the problem, though many modern systems have been upgraded to measure Unix time with signed 64-bit integers which will not overflow for 292 billion years—approximately 21 times the estimated age of the universe.

Cause

Many computer systems measure time and date as Unix time, an international standard for digital timekeeping. Unix time is defined as the number of seconds elapsed since 00:00:00 UTC on 1 January 1970 (an arbitrarily chosen time based on the creation of the first Unix system), which has been dubbed the Unix epoch.

Unix time has historically been encoded as a signed 32-bit integer, a data type composed of 32 binary digits (bits) which represent an integer value, with 'signed' meaning that the number is stored in Two's complement format. Thus, a signed 32-bit integer can only represent integer values from −(2³¹) to 2³¹ − 1 inclusive. Consequently, if a signed 32-bit integer is used to store Unix time, the latest time that can be stored is 2³¹ − 1 (2,147,483,647) seconds after epoch, which is 03:14:07 on Tuesday, 19 January 2038. Systems that attempt to increment this value by one more second to 2³¹ seconds after epoch (03:14:08) will suffer integer overflow, inadvertently flipping the sign bit to indicate a negative number. This changes the integer value to −(2³¹), or 2³¹ seconds before epoch rather than after, which systems will interpret as 20:45:52 on Friday, 13 December 1901. From here, systems will continue to count up, toward zero, and then up through the positive integers again. As many computer systems use time computations to run critical functions, the bug may introduce fatal errors.

Vulnerable systems

Any system using data structures with 32-bit time representations has an inherent risk to fail. A full list of these data structures is virtually impossible to derive, but there are well-known data structures that have the Unix time problem:

File systems that use 32 bits to represent times in inodes
Binary file formats with 32-bit time fields
Databases with 32-bit time fields
Database query languages (such as SQL) that have UNIX_TIMESTAMP()-like commands

Embedded systems

Embedded systems that use dates for either computation or diagnostic logging are most likely to be affected by the Y2038 problem. Despite the modern 18–24 month generational update in computer systems technology, embedded systems are designed to last the lifetime of the machine in which they are a component. It is conceivable that some of these systems may still be in use in 2038. It may be impractical or, in some cases, impossible to upgrade the software running these systems, ultimately requiring replacement if the 32-bit limitations are to be corrected.

Many transportation systems from flight to automobiles use embedded systems extensively. In automotive systems, this may include anti-lock braking system (ABS), electronic stability control (ESC/ESP), traction control (TCS) and automatic four-wheel drive; aircraft may use inertial guidance systems and GPS receivers. Another major use of embedded systems is in communications devices, including cell phones and Internet-enabled appliances (e.g. routers, wireless access points, IP cameras) which rely on storing an accurate time and date and are increasingly based on Unix-like operating systems. For example, the Y2038 problem makes some devices running 32-bit Android crash and not restart when the time is changed to that date.

However, this does not imply that all embedded systems will suffer from the Y2038 problem, since many such systems do not require access to dates. For those that do, those systems which only track the difference between times/dates and not absolute times/dates will, by the nature of the calculation, not experience a major problem. This is the case for automotive diagnostics based on legislated standards such as CARB (California Air Resources Board).

Early problems

In May 2006, reports surfaced of an early manifestation of the Y2038 problem in the AOLserver software. The software was designed with a kludge to handle a database request that should "never" time out. Rather than specifically handling this special case, the initial design simply specified an arbitrary time-out date in the future. The default configuration for the server specified that the request should time out after one billion seconds. One billion seconds (just over 31 years, 251 days, 1 hour, 46 minutes and 40 seconds) after 01:27:28 UTC on 13 May 2006 is beyond the 2038 cutoff date. Thus, after this time, the time-out calculation overflowed and returned a date that was actually in the past, causing the software to crash. When the problem was discovered, AOLServer operators had to edit the configuration file and set the time-out to a lower value.

Solutions

There is no universal solution for the Year 2038 problem. For example, in the C language, any change to the definition of the time_t data type would result in code-compatibility problems in any application in which date and time representations are dependent on the nature of the signed 32-bit time_t integer. For example, changing time_t to an unsigned 32-bit integer, which would extend the range to 2106 (specifically, 06:28:15 UTC on Sunday, 7 February 2106), would adversely affect programs that store, retrieve, or manipulate dates prior to 1970, as such dates are represented by negative numbers. Increasing the size of the time_t type to 64 bits in an existing system would cause incompatible changes to the layout of structures and the binary interface of functions.

Most operating systems designed to run on 64-bit hardware already use signed 64-bit time_t integers. Using a signed 64-bit value introduces a new wraparound date that is over twenty times greater than the estimated age of the universe: approximately 292 billion years from now. The ability to make computations on dates is limited by the fact that tm_year uses a signed 32-bit integer value starting at 1900 for the year. This limits the year to a maximum of 2,147,485,547 (2,147,483,647 + 1900).

Alternative proposals have been made (some of which are already in use), such as storing either milliseconds or microseconds since an epoch (typically either 1 January 1970 or 1 January 2000) in a signed 64-bit integer, providing a minimum range of 300,000 years at microsecond resolution. In particular, Java's use of 64-bit long integers everywhere to represent time as "milliseconds since 1 January 1970" will work correctly for the next 292 million years. Other proposals for new time representations provide different precisions, ranges, and sizes (almost always wider than 32 bits), as well as solving other related problems, such as the handling of leap seconds. In particular, TAI64 is an implementation of the International Atomic Time (TAI) standard, the current international real-time standard for defining a second and frame of reference.

Implemented solutions

Starting with Ruby version 1.9.2, the bug with year 2038 is fixed, by storing time in a signed 64-bit integer on systems with 32-bit time_t.

Starting with NetBSD version 6.0 (released in October 2012), the NetBSD operating system uses a 64-bit time_t for both 32-bit and 64-bit architectures. Applications that were compiled for an older NetBSD release with 32-bit time_t are supported via a binary compatibility layer, but such older applications will still suffer from the Y2038 problem.

OpenBSD since version 5.5, released in May 2014, also uses a 64-bit time_t for both 32-bit and 64-bit architectures. In contrast to NetBSD, there is no binary compatibility layer. Therefore, applications expecting a 32-bit time_t and applications using anything different from time_t to store time values may break.

Linux originally used a 64-bit time_t for 64-bit architectures only; the pure 32-bit ABI was not changed due to backward compatibility. Starting with version 5.6 of 2020, 64-bit time_t is supported on 32-bit architectures, too. This was done primarily for the sake of embedded Linux systems.

FreeBSD uses 64-bit time_t for all 32-bit and 64-bit architectures except 32-bit i386, which uses signed 32-bit time_t instead.

The x32 ABI for Linux (which defines an environment for programs with 32-bit addresses but running the processor in 64-bit mode) uses a 64-bit time_t. Since it was a new environment, there was no need for special compatibility precautions.

Network File System version 4 has defined its time fields as struct nfstime4 {int64_t seconds; uint32_t nseconds;} since December 2000. Values greater than zero for the seconds field denote dates after the 0-hour, January 1, 1970. Values less than zero for the seconds field denote dates before the 0-hour, January 1, 1970. In both cases, the nseconds (nanoseconds) field is to be added to the seconds field for the final time representation.

The ext4 filesystem, when used with inode sizes larger than 128 bytes, has an extra 32-bit field per timestamp, of which 30 bits are used for the nanoseconds part of the timestamp, and the other 2 bits are used to extend the timestamp range to the year 2446.

The XFS filesystem, starting with Linux 5.10, has an optional "big timestamps" feature which extends the timestamp range to the year 2486.

While the native APIs of OpenVMS can support timestamps up to 31 July 31086, the C runtime library (CRTL) uses 32-bit integers for time_t. As part of Y2K compliance work that was carried out in 1998, the CRTL was modified to use unsigned 32-bit integers to represent time; extending the range of time_t up to 7 February 2106.

As of MySQL 8.0.28, the functions FROM_UNIXTIME(), UNIX_TIMESTAMP(), and CONVERT_TZ() handle 64-bit values on platforms that support them. This includes 64-bit versions of Linux, MacOS, and Windows. In relational database versions prior to August 2021, built-in functions like UNIX_TIMESTAMP() will return 0 after 03:14:07 UTC on 19 January 2038.

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