tztab changes for HPUX

Guy Harris guy at
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.

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