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:
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:
2:00
time in hours and minutes
15:00
24-hour format time (for times after noon)
1:28:14
time in hours, minutes, and seconds
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 “wall clock” time,
s if the given time is local “standard” 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 “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
Zone NAME GMTOFF RULES/SAVE FORMAT [UNTILYEAR [MONTH [DAY [TIME]]]]
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, alternatively, 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. Alternatively, a slash (/) separates standard and daylight abbreviations.
UNTILYEAR [MONTH [DAY [TIME]]]
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 fields of a rule; trailing fields can be omitted, and default to the earliest possible value for the missing fields.
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 information in the previous line in the file used by the previous line. Continuation lines may contain
until information, 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 alternative 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) “Stationary” if the leap second time given by the other fields should be interpreted as UTC or (an abbreviation of) “Rolling” if the leap second time given by the other fields should be interpreted as local wall clock time.