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The directory /usr/share/zoneinfo contains a large group of [[tz database| timezone database files|]] files describing both current and historical definitions of local times to facilitate the correct reproduction and translation of time information from one time zone and era to another. The files keep track of the offset from Greenwich Mean Time as well as when seasonal adjustments have been scheduled to take place such as the transition to and from [[Daylight saving time|Daylight Saving Time]] (DST). <ref>{{cite book |last=Ward |first=Brian |date=April 19, 2021 |title=How Linux Works, 3rd Edition |publisher=No Starch Press |section=7.5.1 |isbn=978-1718-500402}} </ref>
==Security==
The integrity of system timestamps are extremely important for fraud detection by keeping track of precisely when financial transactions and other changes occur. By resetting the clock it is possible to misrespresent sequences of events.{{cn|date=Apr 27, 2025}} With that in mind both [[Berkeley Software Distribution|BSD]] and [[GNU]] based Unix systems log both the before and after times when the clock is reset, including by the date command, in the [[utmp]] file.<ref>{{cite web| author=<!-- not stated --> | url=https://www.unix.com/man_page/bsd/5/utmp/https://www.unix.com/man_page/bsd/5/utmp/ | title=bsd man page for utmp| publisher=Unix Linux Community| website=community.unix.com | date=Nov 27, 1996 | date-accessed=April 27, 2025 }}</ref><ref> {{cite web || author=<!-- not stated --> | editor-last=Kerrisk| editor-first=Michael | date= |title= |url=https://man7.org/linux/man-pages/man5/utmp.5.html |website=man7.org | title=utmp(5) — Linux manual page |date=2024-09-91|___location= |publisher= |access-date=April 27, 2025}}</ref>
==History==
David McKenzie is the author of the Linux version of date. The date command has been part of Unix since AT&T's original Version 1.<ref name=Kerrisk /><ref>{{cite web |author=<!-- not stated --> |date=September 10, 2024 |title=FreeBSD Manual Pages |url=https://man.freebsd.org/cgi/man.cgi?date |website=man.freebsd.org |access-date=April 1, 2025}}
==References==
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