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tztab(4)		   Kernel Interfaces Manual		      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  simulta-
       neously 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 Savings"
       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 ad-
       justments 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 num-
       ber  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. pattern.

   International Code Set Support
       Single-byte character code sets are supported.

       The  time zone adjustment table for the Eastern Time Zone in the	United
       States is:

       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 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.

       date(1),	ctime(3C), environ(5).



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