NAME

zic − time zone compiler

SYNOPSIS

zic [ −s ] [ [ −v ] [ −d directory ] [ −l localtime ] [ 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 the filename is ‘−’ or if no filename is specified, the standard input is read.  When standard input is read, zic processes the input lines until a end-of-file character (^D) is encountered. 

Input lines are made up of fields.  Fields are separated by any number of white space characters.  Leading and trailing white space on input lines is ignored.  A pound sign (#) in the input introduces a comment which extends to the end of the line the pound sign appears on.  White space characters and pound signs 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

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.  The word minimum (or an abbreviation) means the minimum year with a representable time value.  The word maximum (or an abbreviation) means the maximum year with a representable time value. 

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 uspres, the rule applies in U.S. Presidential election years; if TYPE is nonpres, the rule applies in years other than U.S. Presidential election years.  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: 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

Any of these forms may be followed by the letter w if the given time is local “wall clock” time or s if the given time is local “standard” time; in the absence of w or s, 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 “variable part” (for example, the “S” or “D” in “EST” or “EDT”) 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

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 GMT 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 GMT. 

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 “variable part” of the time zone abbreviation goes.  UNTIL The time at which the GMT 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 GMT offset and rule change until the time specified. 

The next line must be a “continuation” line; this has the same form as a zone line except that the string “Zone” 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

LinkLINK-FROMLINK-TO
For example:

LinkUS/EasternEST5EDT

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. 

OPTIONS

−s Limit time values stored in output files to values that are the same whether they’re taken to be signed or unsigned. 

−v Complain if a year that appears in a data file is outside the range of years representable by system time values (0:00:00 AM GMT, January 1, 1970, to 3:14:07 AM GMT, January 19, 2038). 

−d directory
Create time conversion information files in the directory directory rather than in the standard directory /usr/lib/locale/TZ. 

−l timezone
Use the time zone timezone as local time.  zic will act as if the file contained a link line of the form

Linktimezone localtime

FILES

/usr/lib/locale/TZ standard directory used for created files

SEE ALSO

time(1), ctime(3)

NOTE

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. 

You can use the time conversion information files zic creates to set the TZ shell variable with the :filename syntax.  (filename is name of a file created by zic.)  For example, to use the time conversion information file US/East-Indiana, enter:

TZ=:US/East-Indiana;export TZ

This syntax can be used by either the shell or can be set system-wide in the file /etc/TIMEZONE.  If the time conversion information files are not in the default directory, the :filename must use a full pathname.  If the :filename is not found, the timezone defaults to GMT.