{ "mode": "man", "parameter": "zic", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/zic/8/json", "generated": "2026-08-11T22:49:49Z", "synopsis": "zic [ option ... ] [ filename ... ]", "sections": { "NAME": { "content": "zic - timezone compiler\n", "subsections": [] }, "SYNOPSIS": { "content": "zic [ option ... ] [ filename ... ]\n", "subsections": [] }, "DESCRIPTION": { "content": "The zic program reads text from the file(s) named on the command line and creates the time‐\nzone information format (TZif) files specified in this input. If a filename is “-”, standard\ninput is read.\n", "subsections": [] }, "OPTIONS": { "content": "--version\nOutput version information and exit.\n\n--help Output short usage message and exit.\n\n-b bloat\nOutput backward-compatibility data as specified by bloat. If bloat is fat, generate\nadditional data entries that work around potential bugs or incompatibilities in older\nsoftware, such as software that mishandles the 64-bit generated data. If bloat is\nslim, keep the output files small; this can help check for the bugs and incompatibili‐\nties. The default is slim, as software that mishandles 64-bit data typically mishan‐\ndles timestamps after the year 2038 anyway. Also see the -r option for another way to\nalter output size.\n\n-d directory\nCreate time conversion information files in the named directory rather than in the\nstandard directory named below.\n\n-l timezone\nUse timezone as local time. zic will act as if the input contained a link line of the\nform\n\nLink timezone localtime\n\nIf timezone is -, any already-existing link is removed.\n\n-L leapsecondfilename\nRead leap second information from the file with the given name. If this option is not\nused, no leap second information appears in output files.\n\n-p timezone\nUse timezone's rules when handling nonstandard TZ strings like \"EET-2EEST\" that lack\ntransition rules. zic will act as if the input contained a link line of the form\n\nLink timezone posixrules\n\nIf timezone is “-” (the default), any already-existing link is removed.\n\nUnless timezone is “-”, this option is obsolete and poorly supported. Among other\nthings it should not be used for timestamps after the year 2037, and it should not be\ncombined with -b slim if timezone's transitions are at standard time or Universal Time\n(UT) instead of local time.\n\n-r [@lo][/@hi]\nLimit the applicability of output files to timestamps in the range from lo (inclusive)\nto hi (exclusive), where lo and hi are possibly signed decimal counts of seconds since\nthe Epoch (1970-01-01 00:00:00 UTC). Omitted counts default to extreme values. The\noutput files use UT offset 0 and abbreviation “-00” in place of the omitted timestamp\ndata. For example, “zic -r @0” omits data intended for negative timestamps (i.e., be‐\nfore the Epoch), and “zic -r @0/@2147483648” outputs data intended only for nonnega‐\ntive timestamps that fit into 31-bit signed integers. On platforms with GNU date,\n“zic -r @$(date +%s)” omits data intended for past timestamps. Although this option\ntypically reduces the output file's size, the size can increase due to the need to\nrepresent the timestamp range boundaries, particularly if hi causes a TZif file to\ncontain explicit entries for pre-hi transitions rather than concisely representing\nthem with an extended POSIX.1-2017 TZ string. Also see the -b slim option for another\nway to shrink output size.\n\n-R @hi Generate redundant trailing explicit transitions for timestamps that occur less than\nhi seconds since the Epoch, even though the transitions could be more concisely repre‐\nsented via the extended POSIX.1-2017 TZ string. This option does not affect the rep‐\nresented timestamps. Although it accommodates nonstandard TZif readers that ignore\nthe extended POSIX.1-2017 TZ string, it increases the size of the altered output\nfiles.\n\n-t file\nWhen creating local time information, put the configuration link in the named file\nrather than in the standard location.\n\n-v Be more verbose, and complain about the following situations:\n\nThe input specifies a link to a link, something not supported by some older parsers,\nincluding zic itself through release 2022e.\n\nA year that appears in a data file is outside the range of representable years.\n\nA time of 24:00 or more appears in the input. Pre-1998 versions of zic prohibit\n24:00, and pre-2007 versions prohibit times greater than 24:00.\n\nA rule goes past the start or end of the month. Pre-2004 versions of zic prohibit\nthis.\n\nA time zone abbreviation uses a %z format. Pre-2015 versions of zic do not support\nthis.\n\nA timestamp contains fractional seconds. Pre-2018 versions of zic do not support\nthis.\n\nThe input contains abbreviations that are mishandled by pre-2018 versions of zic due\nto a longstanding coding bug. These abbreviations include “L” for “Link”, “mi” for\n“min”, “Sa” for “Sat”, and “Su” for “Sun”.\n\nThe output file does not contain all the information about the long-term future of a\ntimezone, because the future cannot be summarized as an extended POSIX.1-2017 TZ\nstring. For example, as of 2023 this problem occurs for Morocco's daylight-saving\nrules, as these rules are based on predictions for when Ramadan will be observed,\nsomething that an extended POSIX.1-2017 TZ string cannot represent.\n\nThe output contains data that may not be handled properly by client code designed for\nolder zic output formats. These compatibility issues affect only timestamps before\n1970 or after the start of 2038.\n\nThe output contains a truncated leap second table, which can cause some older TZif\nreaders to misbehave. This can occur if the -L option is used, and either an Expires\nline is present or the -r option is also used.\n\nThe output file contains more than 1200 transitions, which may be mishandled by some\nclients. The current reference client supports at most 2000 transitions; pre-2014\nversions of the reference client support at most 1200 transitions.\n\nA time zone abbreviation has fewer than 3 or more than 6 characters. POSIX requires\nat least 3, and requires implementations to support at least 6.\n\nAn output file name contains a byte that is not an ASCII letter, “-”, “/”, or “”; or\nit contains a file name component that contains more than 14 bytes or that starts with\n“-”.\n", "subsections": [] }, "FILES": { "content": "/etc/localtime\nDefault local timezone file.\n\n/usr/share/zoneinfo\nDefault timezone information directory.\n", "subsections": [] }, "EXTENDED EXAMPLE": { "content": "Here is an extended example of zic input, intended to illustrate many of its features.\n\n# Rule NAME FROM TO - IN ON AT SAVE LETTER/S\nRule Swiss 1941 1942 - May Mon>=1 1:00 1:00 S\nRule Swiss 1941 1942 - Oct Mon>=1 2:00 0 -\nRule EU 1977 1980 - Apr Sun>=1 1:00u 1:00 S\nRule EU 1977 only - Sep lastSun 1:00u 0 -\nRule EU 1978 only - Oct 1 1:00u 0 -\nRule EU 1979 1995 - Sep lastSun 1:00u 0 -\nRule EU 1981 max - Mar lastSun 1:00u 1:00 S\nRule EU 1996 max - Oct lastSun 1:00u 0 -\n\n# Zone NAME STDOFF RULES FORMAT [UNTIL]\nZone Europe/Zurich 0:34:08 - LMT 1853 Jul 16\n0:29:45.50 - BMT 1894 Jun\n1:00 Swiss CE%sT 1981\n1:00 EU CE%sT\n\nLink Europe/Zurich Europe/Vaduz\n\nIn this example, the EU rules are for the European Union and for its predecessor organiza‐\ntion, the European Communities. The timezone is named Europe/Zurich and it has the alias Eu‐\nrope/Vaduz. This example says that Zurich was 34 minutes and 8 seconds east of UT until\n1853-07-16 at 00:00, when the legal offset was changed to 7 degrees 26 minutes 22.50 seconds,\nwhich works out to 0:29:45.50; zic treats this by rounding it to 0:29:46. After 1894-06-01\nat 00:00 the UT offset became one hour and Swiss daylight saving rules (defined with lines\nbeginning with “Rule Swiss”) apply. From 1981 to the present, EU daylight saving rules have\napplied, and the UTC offset has remained at one hour.\n\nIn 1941 and 1942, daylight saving time applied from the first Monday in May at 01:00 to the\nfirst Monday in October at 02:00. The pre-1981 EU daylight-saving rules have no effect here,\nbut are included for completeness. Since 1981, daylight saving has begun on the last Sunday\nin March at 01:00 UTC. Until 1995 it ended the last Sunday in September at 01:00 UTC, but\nthis changed to the last Sunday in October starting in 1996.\n\nFor purposes of display, “LMT” and “BMT” were initially used, respectively. Since Swiss\nrules and later EU rules were applied, the time zone abbreviation has been CET for standard\ntime and CEST for daylight saving time.\n", "subsections": [] }, "NOTES": { "content": "For areas with more than two types of local time, you may need to use local standard time in\nthe AT field of the earliest transition time's rule to ensure that the earliest transition\ntime recorded in the compiled file is correct.\n\nIf, for a particular timezone, a clock advance caused by the start of daylight saving coin‐\ncides with and is equal to a clock retreat caused by a change in UT offset, zic produces a\nsingle transition to daylight saving at the new UT offset without any change in local (wall\nclock) time. To get separate transitions use multiple zone continuation lines specifying\ntransition instants using universal time.\n", "subsections": [] }, "SEE ALSO": { "content": "tzfile(5), zdump(8)\n\nTime Zone Database zic(8)", "subsections": [] } }, "summary": "zic - timezone compiler", "flags": [], "examples": [], "see_also": [ { "name": "tzfile", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/tzfile/5/json" }, { "name": "zdump", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/zdump/8/json" } ] }