/usr/lib/tztab

[Aleksei_1]

if I make any changes in /usr/lib/tztab about time in which system clocks should be changed to DST will it work?
for example, if i put in EET-2EETDST section month not 9 but 10 will it change time in october not in september?

[Aleksei_1]

yep it works

[Bill Hassell]

/usr/lib/tztab is a very nifty file. HP-UX uses the rules in this file to translate the computer's internal time clock (which is always GMT or more accurately, UTC or Zulu time). HP-UX never jumps the internal time, only the representation after translating it through $TZ which points to tztab. Since daylight saving is a political, not an astronomical concept, there is never an exact definition even within a single country (the U.S. has a 'funny' timezone glitch in Indiana) so tztab allows you to create any daylight saving rules you need.

Note that the kernel has a timezone and dst parameter which are used for daemons or other non-standard programs. The timezone value is in minutes west of GMT and dst has about 6 (not nearly enough) predefined settings. Luckily, no major database vendors or other production applications bypass $TZ but it is useful to set these too.