HP-UX Reference (11i v1 05/09) - 4 File Formats (vol 8)

t
tztab(4) tztab(4)
NAME
tztab - time zone adjustment table for date(1) and ctime(3C)
DESCRIPTION
The tztab file describes the differences between Coordinated Universal Time
(UTC) and local time.
Several local areas can be represented simultaneously with historical detail.
The file
tztab consists of one or more time zone adjustment entries. The first line of the entry contains a
unique string that may match the value of the
TZ string in the user’s environment. The format is
tznamediffdstzname where tzname is the time zone name or abbreviation, diff is the difference in
hours from
UTC, and dstzname is the name or abbreviation of the "Daylight Savings" time zone. Frac-
tional values of diff are expressed in minutes preceded by a colon. Each such string will start with an
alphabetic character.
The second and subsequent lines of each entry details the time zone adjustments for that time zone. The
lines contain seven fields each. The first six fields specify the first minute in which the time zone adjust-
ment, specified in the seventh field, applies. The fields are separated by spaces or tabs. The first six are
integer patterns that specify the minute (0-59), hour (0-23), day of the month (1-31), month of the year (1-
12), year (1970-2038), and day of the week (0-6, with 0=Sunday). The minute, hour, and month of the year
must contain a number in the (respective) range indicated above. The day of the month, year, and day of
the week can contain a number as above or two numbers separated by a minus (indicating an inclusive
range). Either the day of the month or the day of the week field must be a range, the other must be simple
number.
The seventh field is a string that describes the time zone adjustment in its simplest form:
tznamediff
where
tzname is an alphabetic string giving the time zone name or abbreviation, and diff is the difference
in hours from
UTC. tzname must match either the tzname field or the dstzname field in the first
line of the time zone adjustment entry. Any fractional diff is shown in minutes.
Comments begin with a
# in the first column, and include all characters up to a new-line. Comments are
ignored.
If the value of the TZ string does not match any line in the table, it is interpreted according to the current
U.S. pattern.
EXTERNAL INFLUENCES
International Code Set Support
Single-byte character code sets are supported.
EXAMPLES
The time zone adjustment table for the Eastern Time Zone in the United States is:
EST5EDT
0 3 6 1 1974 0-6 EDT4
0 3 22-28 2 1975 0 EDT4
0 3 24-30 4 1976-1986 0 EDT4
0 3 1-7 4 1987-2038 0 EDT4
0 1 24-30 11 1974 0 EST5
0 1 25-31 10 1975-2038 0 EST5
Normally (as indicated in the first line) Eastern Standard Time is five hours earlier than UTC. During Day-
light Savings time, it changes to a 4 hour difference. The first time Daylight Savings Time took effect
(second line) was on January 6, 1974 at 3:00 a.m., EDT. Note that the minute before was 1:59 a.m., EST.
The change back to standard time took effect (sixth line) on the last Sunday in November of the same year.
At that point, the time went from 1:59 a.m. EDT to 1:00 a.m. EST. The transition to Daylight Savings Time
since then has gone from the last Sunday in February (third line) to the last Sunday in April (fourth line) to
the first Sunday in April (fifth line). The return to standard time for the same period has remained at the
last Sunday in October (seventh line).
AUTHOR
tztab was developed by HP.
FILES
/usr/lib/tztab
HP-UX 11i Version 1: September 2005 − 1 − Hewlett-Packard Company Section 4−−367