tztab changes for HPUX
guy at netapp.com
Mon Feb 12 20:05:02 UTC 1996
> Howmsoever...the references to and excerpts from "tztab" files in the articles
> about HPUX indicate the existence of an alternate and (presumably better) way
> of handling time zone stuff. If anyone has tztab insights to share with folks
> on the list, I'd love it.
Better? Maybe, maybe not.
Here's the man page from a machine that's running what claims to be
"HP-UX B.10.00", from "uname -sr":
tztab(4) DEVICES AND NETWORK INTERFACES tztab(4)
tztab - time zone adjustment table for date(1) and ctime(3C)
The file describes the differences between Coordinated
Universal Time (UTC) and local time. Several local areas
can be represented simultaneously with historical detail.
The file 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 where is the time zone
name or abbreviation, diff is the difference in hours from
UTC, and is the name or abbreviation of the "Daylight Sav-
ings" time zone. Fractional 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 adjustment, 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: where is an alphabetic
string giving the time zone name or abbreviation, and diff
is the difference in hours from UTC. must match either the
field or the 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 string does not match any line in the
table, it is interpreted according to the current U.S. pat-
The time zone adjustment table for the Eastern Time Zone in
the United States is:
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 Janu-
ary 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).
was developed by HP.
More information about the tz