tztab.4 (2010 09)

t
tztab(4) tztab(4)
NAME
tztab - time zone adjustment table for date and ctime()
DESCRIPTION
The
/usr/lib/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 newline. Comments are
ignored.
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
Daylight 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 Sav-
ings 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
SEE ALSO
date(1), ctime(3C), environ(5).
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1