ZIC(8)

NAME
zic - time zone compiler

SYNOPSIS
zic [ --version ] [ -v ] [ -d directory ] [ -l localtime ] [ -p posixrules ] [ -L leapsecondfilename ] [ -s ] [ -y command ] [ filename ... ]

DESCRIPTION
Zic reads text from the file(s) named on the command line and creates the time conversion information files specified in this input. If a filename is -, the standard input is read.

These options are available:

--version
    Output version information and exit.

-d directory
    Create time conversion information files in the named directory rather than in the standard directory named below.

-l timezone
    Use the given time zone as local time. Zic will act as if the input contained a link line of the form

    Link    timezone    localtime

-p timezone
    Use the given time zone's rules when handling POSIX-format time zone environment variables. Zic will act as if the input contained a link line of the form

    Link    timezone    posixrules

-L leapsecondfilename
    Read leap second information from the file with the given name. If this option is not used, no leap second information appears in output files.

-v  Complain if a year that appears in a data file is outside the range of years representable by time(2) values. Also complain if a time of 24:00 (which cannot be handled by pre-1998 versions of zic) appears in the input.

-s  Limit time values stored in output files to values that are the same whether they're taken to be signed or unsigned. You can use this option to generate SVVS-compatible files.

-y command
    Use the given command rather than yearistype when checking year types (see below).

Input lines are made up of fields. Fields are separated from one another by any number of white space characters. Leading and trailing white space on input lines is ignored. An unquoted sharp character (#) in the input introduces a comment which extends to the end of the line the sharp character appears on. White space characters and sharp characters may be enclosed in double quotes (") if they're to be used as part of a field. Any line that is blank (after comment stripping) is ignored. Non-blank lines are expected to be of one of three types: rule lines, zone lines, and link lines.

A rule line has the form

Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S

For example:

Rule	US	1967	1973	-	Apr	lastSun	2:00	1:00	D

The fields that make up a rule line are:

NAME
    Gives the (arbitrary) name of the set of rules this rule is part of.

FROM
    Gives the first year in which the rule applies. Any integer year can be supplied; the Gregorian calendar is assumed. The word minimum (or an abbreviation) means the minimum year representable as an integer. The word maximum (or an abbreviation) means the maximum year representable as an integer. Rules can describe times that are not representable as time values, with the unrepresentable times ignored; this allows rules to be portable among hosts with differing time value types.

TO  Gives the final year in which the rule applies. In addition to minimum and maximum (as above), the word only (or an abbreviation) may be used to repeat the value of the FROM field.

TYPE
    Gives the type of year in which the rule applies. If TYPE is - then the rule applies in all years between FROM and TO inclusive. If TYPE is something else, then zic executes the command
    yearistype year type
    to check the type of a year: an exit status of zero is taken to mean that the year is of the given type; an exit status of one is taken to mean that the year is not of the given type.

IN  Names the month in which the rule takes effect. Month names may be abbreviated.

ON  Gives the day on which the rule takes effect. Recognized forms include:

    5	the fifth of the month
    lastSun	the last Sunday in the month
    lastMon	the last Monday in the month
    Sun>=8	first Sunday on or after the eighth
    Sun<=25	last Sunday on or before the 25th

    Names of days of the week may be abbreviated or spelled out in full. Note that there must be no spaces within the ON field.

AT  Gives the time of day at which the rule takes effect. Recognized forms include:

    2	time in hours
    2:00	time in hours and minutes
    15:00	24-hour format time (for times after noon)
    1:28:14	time in hours, minutes, and seconds
    -	equivalent to 0

    where hour 0 is midnight at the start of the day, and hour 24 is midnight at the end of the day. Any of these forms may be followed by the letter w if the given time is local time, s if the given time is local time, or u (or g or z) if the given time is universal time; in the absence of an indicator, wall clock time is assumed.

SAVE
    Gives the amount of time to be added to local standard time when the rule is in effect. This field has the same format as the AT field (although, of course, the w and s suffixes are not used).

LETTER/S
    Gives the (for example, the or in or of time zone abbreviations to be used when this rule is in effect. If this field is -, the variable part is null.

A zone line has the form

Zone	NAME	GMTOFF	RULES/SAVE	FORMAT	[UNTIL]

For example:

Zone	Australia/Adelaide	9:30	Aus	CST	1971 Oct 31 2:00

The fields that make up a zone line are:

NAME
    The name of the time zone. This is the name used in creating the time conversion information file for the zone.

GMTOFF
    The amount of time to add to UTC to get standard time in this zone. This field has the same format as the AT and SAVE fields of rule lines; begin the field with a minus sign if time must be subtracted from UTC.

RULES/SAVE
    The name of the rule(s) that apply in the time zone or, alternately, an amount of time to add to local standard time. If this field is - then standard time always applies in the time zone.

FORMAT
    The format for time zone abbreviations in this time zone. The pair of characters %s is used to show where the of the time zone abbreviation goes. Alternately, a slash (/) separates standard and daylight abbreviations.

UNTIL
    The time at which the UTC offset or the rule(s) change for a location. It is specified as a year, a month, a day, and a time of day. If this is specified, the time zone information is generated from the given UTC offset and rule change until the time specified. The month, day, and time of day have the same format as the IN, ON, and AT columns of a rule; trailing columns can be omitted, and default to the earliest possible value for the missing columns.

    The next line must be a line; this has the same form as a zone line except that the string and the name are omitted, as the continuation line will place information starting at the time specified as the UNTIL field in the previous line in the file used by the previous line. Continuation lines may contain an UNTIL field, just as zone lines do, indicating that the next line is a further continuation.

A link line has the form

Link	LINK-FROM	LINK-TO

For example:

Link	Europe/Istanbul	Asia/Istanbul

The LINK-FROM field should appear as the NAME field in some zone line; the LINK-TO field is used as an alternate name for that zone.

Except for continuation lines, lines may appear in any order in the input.

Lines in the file that describes leap seconds have the following form:

Leap	YEAR	MONTH	DAY	HH:MM:SS	CORR	R/S

For example:

Leap	1974	Dec	31	23:59:60	+	S

The YEAR, MONTH, DAY, and HH:MM:SS fields tell when the leap second happened. The CORR field should be if a second was added or if a second was skipped. The R/S field should be (an abbreviation of) if the leap second time given by the other fields should be interpreted as UTC or (an abbreviation of) if the leap second time given by the other fields should be interpreted as local wall clock time.

NOTES
For areas with more than two types of local time, you may need to use local standard time in the AT field of the earliest transition time's rule to ensure that the earliest transition time recorded in the compiled file is correct.

If, for a particular zone, a clock advance caused by the start of daylight saving coincides with and is equal to a clock retreat caused by a change in UTC offset, zic produces a single transition to daylight saving at the new UTC offset (without any change in wall clock time). To get separate transitions use multiple zone continuation lines specifying transition instants using universal time.

FILE
/usr/share/zoneinfo    standard directory used for created files

SEE ALSO
newctime(3), tzfile(5), zdump(8)