Wikipedia

Year 2038 problem

Theyear 2038 problem(also known asY2038,[1]Y2K38,Y2K38 superbugor theEpochalypse[2][3]) is atime computing problemthat leaves some computer systems unable to represent times after 03:14:07UTCon 19 January 2038.

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

The problem exists in systems which measureUnix time—the number of seconds elapsed since theUnixepoch(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) and231− 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 231secondsbeforeepoch (20:45:52 UTC on 13 December 1901). The problem is similar in nature to theyear 2000 problem,the difference being the Year 2000 problem had to do withbase 10 numbers,whereas the Year 2038 problem involvesbase 2 numbers.

Analogous storage constraints will be reached in2106,where systems storing Unix time as anunsigned(rather than signed) 32-bit integer will overflow on 7 February 2106 at 06:28:15 UTC.

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 aslegacyandembedded systems.Modern systems and software updates to legacy systems address this problem by using signed64-bitintegers instead of 32-bit integers, which will take 292 billion years to overflow—approximately 21 times the estimatedage of the universe.

Cause

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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 since 00:00:00UTCon 1 January 1970 (an arbitrarily chosen time based on the creation of the firstUnix system), which has been dubbed theUnix epoch.[6]

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 complementformat.[a]Thus, a signed 32-bit integer can only represent integer values from −(231) to231− 1inclusive. 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.[7]Systems that attempt to increment this value by one more second to 231seconds 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 231secondsbeforeepoch rather thanafter,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 serious problems.

Vulnerable systems

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Any system usingdata structureswith 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:

  • File systems that use 32 bits to represent times ininodes
  • Binary file formats with 32-bit time fields
  • Databases with 32-bit time fields
  • Database query languages (such asSQL) that haveUNIX_TIMESTAMP()-like commands

Embedded systems

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Embedded systemsthat 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 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 includeanti-lock braking system(ABS),electronic stability control(ESC/ESP),traction control(TCS) and automaticfour-wheel drive;aircraft may useinertial guidance systemsandGPS receivers.[b]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-bitAndroidcrash and not restart when the time is changed to that date.[8]

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).[9]

Early problems

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In May 2006, reports surfaced of an early manifestation of the Y2038 problem in theAOLserversoftware. The software was designed with akludgeto handle a database request that should "never" time out. Rather than specifically handling this special case, the initial design simply specified an arbitrarytime-outdate 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]

Solutions

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There is no universal solution for the Year 2038 problem. For example, in theC language,any change to the definition of thetime_tdata type would result incode-compatibilityproblems in any application in which date and time representations are dependent on the nature of the signed 32-bittime_tinteger. For example, changingtime_tto an unsigned 32-bit integer, which would extend the range to 2106[10](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_ttype 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-bithardwarealready use signed 64-bittime_tintegers. 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.[11]The ability to makecomputationson dates is limited by the fact thattm_yearuses 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).[12]

Alternative proposals have been made (some of which are already in use), such as storing eithermillisecondsormicrosecondssince 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.[13][14]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 ofleap seconds.In particular, TAI64[15]is an implementation of theInternational Atomic Time(TAI) standard, the current international real-time standard for defining a second and frame of reference.

Implemented solutions

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  • Starting withRubyversion 1.9.2 (released on 18 August 2010), the bug with year 2038 is fixed,[16]by storing time in a signed 64-bit integer on systems with 32-bittime_t.[17]
  • Starting withNetBSDversion 6.0 (released in October 2012), the NetBSD operating system uses a 64-bittime_tfor both 32-bit and 64-bit architectures. Applications that were compiled for an older NetBSD release with 32-bittime_tare supported via a binary compatibility layer, but such older applications will still suffer from the Y2038 problem.[18]
  • OpenBSDsince version 5.5, released in May 2014, also uses a 64-bittime_tfor both 32-bit and 64-bit architectures. In contrast toNetBSD,there is no binary compatibility layer. Therefore, applications expecting a 32-bittime_tand applications using anything different fromtime_tto store time values may break.[19]
  • Linuxoriginally used a 64-bittime_tfor 64-bit architectures only; the pure 32-bitABIwas not changed due to backward compatibility.[20]Starting with version5.6of 2020, 64-bittime_tis supported on 32-bit architectures, too. This was done primarily for the sake ofembedded Linuxsystems.[21]
  • GNU C Librarysince version 2.34 (released August 2021), added support for using 64-bittime_ton 32-bit platforms with appropriate Linux versions. This support can be activated by defining preprocessor macro_TIME_BITSto64when compiling source code.[22]
  • FreeBSDuses 64-bittime_tfor all 32-bit and 64-bit architectures except 32-bit i386, which uses signed 32-bittime_tinstead.[23]
  • Thex32 ABIfor Linux (which defines an environment for programs with 32-bit addresses but running the processor in 64-bit mode) uses a 64-bittime_t.Since it was a new environment, there was no need for special compatibility precautions.[20]
  • Network File Systemversion 4 has defined its time fields asstruct nfstime4 {int64_t seconds; uint32_t nseconds;}since December 2000.[24]Version 3 supports unsigned 32-bit values asstruct nfstime3 {uint32 seconds; uint32 nseconds;};.[25]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.
  • Theext4filesystem, 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.[26]
  • TheXFSfilesystem, starting with Linux 5.10, has an optional "big timestamps" feature which extends the timestamp range to the year 2486.[27]
  • While the native APIs ofOpenVMScan support timestamps up to 31 July 31086,[28]the C runtime library (CRTL) uses 32-bit integers fortime_t.[29]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_tup to 7 February 2106.[30]
  • PostgreSQLsince version 7.2, released 2002-02-04, stores timestamp WITHOUT TIMEZONE as 64-bit.[31][failed verification]Prior versions already stored timestamp as 64-bit.[citation needed]
  • As ofMySQL8.0.28, released in January 2022, the functionsFROM_UNIXTIME(),UNIX_TIMESTAMP(),andCONVERT_TZ()handle 64-bit values on platforms that support them. This includes 64-bit versions of Linux, macOS, and Windows.[32][33]In older versions, built-in functions likeUNIX_TIMESTAMP()will return 0 after 03:14:07UTCon 19 January 2038.[34]
  • As ofMariaDB11.5.1, released in May 2024, the data typeTIMESTAMPand functionsFROM_UNIXTIME(),UNIX_TIMESTAMP(),andCONVERT_TZ()handle unsigned 32-bit values on 64-bit versions of Linux, macOS, and Windows.[35]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.
  • Starting withVisual C++2005, the CRT uses a 64-bittime_tunless the_USE_32BIT_TIME_Tpreprocessor macro is defined.[36]However, theWindows APIitself is unaffected by the year 2038 bug, asWindowsinternally 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.[37]

See also

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Notes

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  1. ^Unless otherwise specified, all the numbers provided in this article have been derived using two's complement for signed integer arithmetic.
  2. ^GPS suffers its own time counter overflow problem known asGPS Week Number Rollover.

References

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  1. ^ab"Is the Year 2038 problem the new Y2K bug?".The Guardian.17 December 2014.Archivedfrom the original on 25 January 2022.Retrieved11 October2018.
  2. ^Bergmann, Arnd (6 February 2020)."The end of an Era".Linaro.Archivedfrom the original on 7 February 2020.Retrieved13 September2020.
  3. ^Wagenseil, Paul (28 July 2017)."Digital 'Epochalypse' Could Bring World to Grinding Halt".Tom's Guide.Archivedfrom the original on 29 November 2021.Retrieved13 September2020.
  4. ^ab"The Future Lies Ahead".28 June 2006.Archivedfrom the original on 28 November 2006.Retrieved19 November2006.
  5. ^abWeird "memory leak" problem in AOLserver 3.4.2/3.xArchived4 January 2010 at theWayback Machine12 May 2006
  6. ^"Epoch Time".unixtutoria.15 March 2019.Archivedfrom the original on 13 April 2023.Retrieved13 April2023.
  7. ^Diomidis Spinellis (2006).Code quality: the open source perspective.Effective software development series inSafari Books Online(illustrated ed.).Adobe Press.p. 49.ISBN978-0-321-16607-4.
  8. ^"ZTE Blade running Android 2.2 has 2038 problems".Archivedfrom the original on 19 May 2022.Retrieved20 November2018.
  9. ^"ARB Test Methods / Procedures".ARB.ca.gov.California Air Resources Board.Archived fromthe originalon 18 November 2016.Retrieved12 September2013.
  10. ^"DRAFT: Y2038 Proofness Design".Archivedfrom the original on 21 September 2019.Retrieved25 May2024.
  11. ^"When does the 64-bit Unix time_t really end?".Archivedfrom the original on 23 September 2022.Retrieved24 September2022.
  12. ^Felts, Bob (17 April 2010)."The End of Time".Stablecross.Archivedfrom the original on 11 October 2012.Retrieved19 March2012.
  13. ^"Unununium Time".Archived fromthe originalon 8 April 2006.Retrieved19 November2006.
  14. ^Sun Microsystems."Java API documentation for System.currentTimeMillis()".Archivedfrom the original on 30 September 2017.Retrieved29 September2017.
  15. ^"TAI64".Archivedfrom the original on 26 September 2012.Retrieved4 September2012.
  16. ^"Ruby 1.9.2 is released".18 August 2010.Archivedfrom the original on 8 April 2022.Retrieved1 April2022.
  17. ^"time.c: use 64bit arithmetic even on platforms with 32bit VALUE".GitHub.Archivedfrom the original on 3 November 2023.Retrieved3 November2023.
  18. ^"Announcing NetBSD 6.0".17 October 2012.Archivedfrom the original on 15 January 2016.Retrieved18 January2016.
  19. ^"OpenBSD 5.5 released (May 1, 2014)".1 May 2014.Archivedfrom the original on 22 December 2015.Retrieved18 January2016.
  20. ^abJonathan Corbet(14 August 2013)."Pondering 2038".LWN.net.Archivedfrom the original on 4 March 2016.Retrieved9 March2016.
  21. ^"LKML: Arnd Bergmann: [GIT PULL] y2038: core, driver and file system changes".lkml.org.Archivedfrom the original on 14 February 2020.Retrieved30 January2020.
  22. ^O'Donell, Carlos (2 August 2021)."The GNU C Library version 2.34 is now available".Sourceware.Archivedfrom the original on 30 April 2024.Retrieved30 April2024.
  23. ^"arch".freebsd.org.Archivedfrom the original on 26 September 2018.Retrieved26 September2018.
  24. ^Haynes, Thomas; Noveck, David, eds. (March 2015)."Structured Data Types".Network File System (NFS) Version 4 Protocol.sec. 2.2.doi:10.17487/RFC7530.RFC7530.
  25. ^Staubach, Peter; Pawlowski, Brian; Callaghan, Brent (June 1995)."NFS Version 3 Protocol Specification".Retrieved25 May2024.
  26. ^"ext4 Data Structures and Algorithms".Archivedfrom the original on 13 September 2022.Retrieved13 September2022.
  27. ^Michael Larabel (15 October 2020)."XFS File-System With Linux 5.10 Punts Year 2038 Problem To The Year 2486".Phoronix.Archivedfrom the original on 13 September 2022.Retrieved13 September2022.
  28. ^"Why is Wednesday, November 17, 1858 the base time for OpenVMS (VAX VMS)?".Stanford University.24 July 1997.Archivedfrom the original on 24 July 1997.Retrieved8 January2020.
  29. ^"VSI C Run-Time Library Reference Manual for OpenVMS Systems"(PDF).VSI. November 2020. Archived fromthe original(PDF)on 17 April 2021.Retrieved17 April2021.
  30. ^"OpenVMS and the year 2038".HP.Archivedfrom the original on 17 April 2021.Retrieved17 April2021.
  31. ^"PostgreSQL Release 7.2".January 2012.Archivedfrom the original on 26 April 2024.Retrieved25 April2024.
  32. ^"What Is New in MySQL 8.0".dev.mysql.
  33. ^"Changes in MySQL 8.0.28 (2022-01-18, General Availability)".dev.mysql.Archivedfrom the original on 8 December 2023.Retrieved14 May2024.
  34. ^"MySQL Bugs: #12654: 64-bit unix timestamp is not supported in MySQL functions".bugs.mysql.Archivedfrom the original on 29 March 2017.Retrieved28 March2017.
  35. ^"MariaDB 11.5.1 Release Notes".
  36. ^"Microsoft C/C++ change history 2003 - 2015".learn.microsoft.25 May 2023.Retrieved13 August2024.
  37. ^"About Time - Win32 apps".learn.microsoft.7 January 2021.Retrieved13 August2024.
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