tzfile(5) File Formats Manual tzfile(5) (NAME) tzfile - () (DESCRIPTION) (timezone) tzset(3) /usr/share/zoneinfo . RFC 9636 . . (big- endian ) (two's complement) () () . : o (ASCII) "TZif" . o ( NUL "2" "3" "4"). o . o : tzh_ttisutcnt UT/ . (UT Universal Time .) tzh_ttisstdcnt / . tzh_leapcnt . tzh_timecnt . tzh_typecnt ( ). tzh_charcnt . : o tzh_timecnt . . ( time(2) ) . o tzh_timecnt ( ) . ( TZ .) . o tzh_typecnt ttinfo : struct ttinfo { int32_t tt_utoff; unsigned char tt_isdst; unsigned char tt_desigidx; }; tt_utoff tt_isdst tt_desigidx . tt_utoff UT tt_isdst tm_isdst localtime(3) tt_desigidx ttinfo "-00" ttinfo . tt_utoff -2**31 . tt_utoff [-89999, 93599] ( -25 26 ) POSIX [-24:59:59, 25:59:59] . o tzh_charcnt (null-terminated) tt_desigidx . . . o tzh_leapcnt ( time(2) ) . . ( ) . UTC . -1 . -1 ( ). o tzh_ttisstdcnt / ( ) . o tzh_ttisutcnt UT/ UT . UT/ / . / UT/ TZif TZ . TZ="EET-2EEST" TZif "EET-2EEST" TZif "posixrules" "Europe/Brussels" ( UT ) . POSIX ( ) TZ="Europe/Athens" POSIX.1-2017 TZ="EET-2EEST,M3.5.0/3,M10.5.0/4" . localtime(3) tzh_timecnt ttinfo . (Version 2 format) . ( .) (newline) TZ . TZ ( ). TZ ( ) "WET0WEST,M3.5.0/1,M10.5.0" "WEST" UT . TZ UT TZif . ( ) . (Version 3 format) TZ ( newtzset(3)) POSIX.1-2024 POSIX.1-2017 : TZ="<-02>2<-01>,M3.5.0/-1,M10.5.0/0" -167 167 . TZ="XXX3EDT4,0/0,J365/23" 00:00 24:00 (DST) . (Version 4 format) TZif +1 -1 TZif . . (Interoperability considerations) . . . . . TZ . . . tzh_timecnt . TZif TZif ( ). () () "-" "+" . POSIX . UT . "+0530" UT UT "-00" UT . . . . UTC UTC . (Common interoperability issues) TZif . TZif . : o TZif TZif o TZif TZif o TZif . TZif TZif . . . TZif : o . . . o POSIX.1-2024 POSIX.1-2017 TZ . . o UT TZ . TZ . o 24:00 - TZ "EST5EDT,0/0,J365/25" (-04) . "XXX3EDT4,0/0,J365/23" (XXX, -03) (EDT, -04) . - "AST4" (-04). o RFC 9636 . o . . o TZ . TZ="Africa/Casablanca" . TZif TZ "<+01>-1" . o (heuristic) . () . o -2**31 . . -2**31 . o . -2**59 . o TZ "<" ">" . "<" ">" . o . . o "-" "+" . . o TZif UT UT . TZ "IST-1GMT0,M10.5.0,M3.5.0/1" (IST, +01) (GMT, +00) . TZ "GMT0IST,M3.5.0/1,M10.5.0" . UT . o UTC . UTC +01:23:45 78796801 (1972-06-30 23:59:60 UTC) 78796800 78796801 01:23:46 01:23:45 78796815 01:23:60 01:23:59 . UTC . . o . . o . . o "-08" "+" "-" . o UT -12 +12 (Kiritimati) . o UT [-3599, -1] UT "+00" . o UT . (SEE ALSO) time(2), localtime(3), tzset(3), tzselect(8), zdump(8), zic(8). Olson A, Eggert P, Murchison K. The Time Zone Information Format (TZif). October 2024. Internet RFC 9636 doi:10.17487/RFC9636 . Time Zone Database tzfile(5)