Theyear 2038 problem (also known asY2038,[1]Y2K38,Y2K38 superbug, or theEpochalypse[2][3]) is atime computing problem that leaves some computer systems unable to represent times after 03:14:07UTC on 19 January 2038.
The problem exists in systems which measureUnix time—the number of seconds elapsed since the Unixepoch (00:00:00 UTC on 1 January 1970)—and store it in asigned 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 theinteger to overflow, setting its value to −(231) which systems will interpret as 231 secondsbefore epoch (20:45:52 UTC on 13 December 1901). Systems usingunsigned 32-bit integers will overflow in2106. The problem resembles theyear 2000 problem but arises from limitations inbase-2 (binary) time representation, rather thanbase-10.
Computer systems that use time for critical computations may encounter fatal errors if the year 2038 problem is not addressed. Some applications that use future dates have already encountered the bug.[4][5] The most vulnerable systems are those which are infrequently or never updated, such aslegacy andembedded systems. Modern systems and software updates to legacy systems address this problem by using signed64-bit integers instead of 32-bit integers, which will take 292 billion years to overflow—approximately 21 times the estimatedage of the universe.[6]
Many computer systems measure time and date usingUnix time, an international standard for digital timekeeping. Unix time is defined as the number of seconds elapsed, ignoringleap seconds, since 00:00:00UTC on 1 January 1970, known as theUnix epoch.
Unix time has historically been encoded as asigned 32-bit integer, a data type composed of 32binary digits (bits) which represent an integer value, with 'signed' meaning that the number can represent both positive and negative numbers, as well as zero; and is usually stored intwo's complement format.[a] 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)[b] seconds after epoch, which is 03:14:07 UTC on 19 January 2038.[7] Systems that attempt to increment this value by one more second to 231 seconds after epoch (03:14:08) will sufferinteger overflow, inadvertently flipping the sign bit to indicate a negative number. This changes the integer value to −(231), or 231 secondsbefore epoch rather thanafter, which systems will interpret as 20:45:52 UTC on 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 serious problems.
Any system usingdata structures with signed 32-bit time representations has an inherent risk of failing. 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:
UNIX_TIMESTAMP()-like commands._gmtime32 format (which serves as a mapping oftime_t's 32-bit version) roll over at 19 January 2038 00:00:00. Software built with pre-2005 versions of Visual Studio were known to have_gmtime correspond to_gmtime32, and the correspondence can be forced when building with 32-bit versions of Visual Studio through Visual Studio 2019 by specifying_USE_32BIT_TIME_T.[14]Embedded systems that use dates for either computation or diagnostic logging are most likely to be affected by the Y2038 problem.[1] Despite the modern18–24 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 difficult 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 includeanti-lock braking system (ABS),electronic stability control (ESC/ESP),traction control (TCS), and automaticfour-wheel drive; aircraft may useinertial guidance systems andGPS receivers.[c]
Another major use of embedded systems is in communications devices, includingcell 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.
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).[15]
In May 2006, reports surfaced of an early manifestation of the Y2038 problem in theAOLserver software. The software was designed with akludge to handle a database request that should "never" time out. Rather than specifically handling this special case, the initial design simply specified an arbitrarytime-out date in the future with a default configuration specifying that requests should time out after a maximum of one billion seconds. However, one billion seconds before the 2038 cutoff date is 01:27:28 UTC on 13 May 2006, so requests sent after this time would result in a time-out date which is beyond the cutoff. This made time-out calculations overflow and return dates that were actually in the past, causing 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.[4][5]
Many types of self-signedCA certificates generated on 32-bit systems can have very long expiration dates that go beyond the rollover point, which will make them not work correctly, affectingHTTPS verifications on services (for instanceVPNs) and sites that use them.[16]
The MS Filtering Engine Update anti-malware functions ofMicrosoft Exchange Server installations broke on January 1, 2022 after an update. The functions mapped the processed UpdateVersion numbers (which used a 9- or 10-digit YY-MM-DD-n format) to the Unix time stamp numbers despite their times being very different, so when the engine received the 220101001 (22-01-01 v001) update, which it took to mean 2201010001 with an extra zero near the end, it tried mapping it to the 32-bit Unix time's number and failed due to being higher than 2147483647.[17] Affected Exchange servers failed to work unless they turned off the anti-malware functions, and an automated fix was published on January 5, 2022.
InOracle Access Management version 10.1.4.3 for Windows, the Identity Console component sets a cookie containingUI preferences with an expiry of 500,000,000 seconds in the future (approximately 15 years, 312 days). This is beyond 19 January 2038 and so it throws anexception for certain search activities after 02:20:48 UTC on 17 March 2022 because thegmtime_r() call cannot convert the number provided to a date to write to the cookie.[18]
Some versions ofWindows Media Player Legacy refuse to run or be set up if the system time is on or after January 1, 2038.[19]
There is no universal solution for the Year 2038 problem. For example, in theC language, any change to the definition of thetime_t data type would result incode-compatibility problems in any application in which date and time representations are dependent on the nature of the signed 32-bittime_t integer. Changingtime_t to an unsigned 32-bit integer, which would extend the range to 2106[20] (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 thetime_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-bithardware already use signed 64-bittime_t integers. Using a signed 64-bit value introduces a new wraparound date that is over twenty times greater than the estimatedage of the universe: approximately 292 billion years from now.[21] The ability to makecomputations on dates is limited by the fact thattm_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).[22]
Alternative proposals have been made (some of which are already in use), such as storing eithermilliseconds ormicroseconds since an epoch (typically either 1 January 1970 or 1 January 2000) in a signed 64-bit integer, providing a minimum range of 292,000 years at microsecond resolution.[23][24] In particular, Java's and JavaScript's use of 64-bit signed integers to represent absolute timestamps as "milliseconds since 1 January 1970" will work correctly for the next292 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 ofleap seconds. In particular, TAI64[25] is an implementation of theInternational Atomic Time (TAI) standard, the current international real-time standard for defining a second and frame of reference.
time_t.[27]time_t for both 32-bit and 64-bit architectures. Applications that were compiled for an older NetBSD release with 32-bittime_t are supported via a binary compatibility layer, but such older applications will still suffer from the Y2038 problem.[28]time_t for both 32-bit and 64-bit architectures. In contrast toNetBSD, there is no binary compatibility layer. Therefore, applications expecting a 32-bittime_t and applications using anything different fromtime_t to store time values may break.[29]time_t for 64-bit architectures only; the pure 32-bitABI was not changed due to backward compatibility.[30] Starting with version5.6 of 2020, 64-bittime_t is supported on 32-bit architectures, too. This was done primarily for the sake ofembedded Linux systems.[31]time_t on 32-bit platforms with appropriate Linux versions. This support can be activated by defining preprocessor macro_TIME_BITS to64 when compiling source code.[32]time_t for all 32-bit and 64-bit architectures except 32-bit i386, which uses signed 32-bittime_t instead.[33]time_t. Since it was a new environment, there was no need for special compatibility precautions.[30]struct nfstime4 {int64_t seconds; uint32_t nseconds;} since December 2000.[34] Version 3 supports unsigned 32-bit values asstruct nfstime3 {uint32 seconds; uint32 nseconds;};.[35] 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.time_t.[39] 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 oftime_t up to 7 February 2106.[40]FROM_UNIXTIME(),UNIX_TIMESTAMP(), andCONVERT_TZ() handle 64-bit values on platforms that support them. This includes 64-bit versions of Linux, macOS, and Windows.[41][42] In older versions, built-in functions likeUNIX_TIMESTAMP() will return 0 after 03:14:07UTC on 19 January 2038.[43]TIMESTAMP and functionsFROM_UNIXTIME(),UNIX_TIMESTAMP(), andCONVERT_TZ() handle unsigned 32-bit values on 64-bit versions of Linux, macOS, and Windows.[44] This extended the range to 2106-02-07 06:28:15 and allowed users to store such timestamp values in tables without changing the storage layout and thus staying fully compatible with existing user data.time_t unless the_USE_32BIT_TIME_T preprocessor macro is defined.[45] However, theWindows API itself is unaffected by the year 2038 bug, asWindows internally tracks time as the number of 100-nanosecond intervals since 1 January 1601 in a 64-bit signed integer, which will not overflow until year30,828.[46]_USE_32BIT_TIME_T, and it has not been allowed when building with 64-bit versions of Visual Studio.[14]
