time zone offset definitions.

hellolqs · 08-31-2011, 03:24 PM

Hello,

I have a question about time zone offset in Linux.

Since Linux supports all different Time zones and DSTs, each of the time zone offset constants, for example EST/PST/CST/MST, should have been defined somewhere such as a header file or, other mechanisms may be used by Linux.

Could anyone help to provide some information?

Appreciated!!

tronayne · 08-31-2011, 03:40 PM

They're pretty much all found in /usr/share/zoneinfo, particularly the file /usr/share/zoneinfo/localtime (a symbolic link to /etc/localtime).

When you installed your distribution you were asked what time zone to use and that got set for you.

It's worth a look a the timezone manual page for more information.

Hope this helps some.

michaelk · 08-31-2011, 03:58 PM

And
http://en.wikipedia.org/wiki/Tz_database

hellolqs · 08-31-2011, 06:12 PM

Quote:

Originally Posted by tronayne

They're pretty much all found in /usr/share/zoneinfo, particularly the file /usr/share/zoneinfo/localtime (a symbolic link to /etc/localtime).

When you installed your distribution you were asked what time zone to use and that got set for you.

It's worth a look a the timezone manual page for more information.

Hope this helps some.

Thank you! tronayne and Michael,

Sorry I did not mention that it is in an embedded environment and I realized that /usr/share/zoneinfo and /etc/localtime are actually not supported.

Just curious, could there be a header file which contains the constant definitions for time zone offsets?
Or, a Clib or system function that convert between the time zone offset value and a time zone name?

Thanks again.

tronayne · 09-01-2011, 06:58 AM

Perhaps you can do it the old-fashioned way by setting the TZ environment variable? You do not indicate where you are in the world but, for example, the eastern time zone in the United States is defined as

Code:

EST5EDT

where the EST is Eastern Standard Time, 5 is the difference to UTC during standard time, and EDT indicate that stupid... uh, daylight savings time is in use.

You can find an overview at http://en.wikipedia.org/wiki/Tz_database, and you can find the table of time zone information at http://en.wikipedia.org/wiki/List_of...ase_time_zones (if you had /usr/share/zoneinfo/zone.tab available, that's what the Wikipedia article is talking about).

Embedded system? I dunno if setting TZ will do any good (and, of course, you've got to have the proper offset and a way to figure out when or if daylight time goes into effect) or you just set your system clock to UTC and be done with it, eh?

Hope this helps some.

hellolqs · 09-01-2011, 08:55 AM

Quote:

Originally Posted by tronayne

Perhaps you can do it the old-fashioned way by setting the TZ environment variable? You do not indicate where you are in the world but, for example, the eastern time zone in the United States is defined as

Code:

EST5EDT

where the EST is Eastern Standard Time, 5 is the difference to UTC during standard time, and EDT indicate that stupid... uh, daylight savings time is in use.

You can find an overview at http://en.wikipedia.org/wiki/Tz_database, and you can find the table of time zone information at http://en.wikipedia.org/wiki/List_of...ase_time_zones (if you had /usr/share/zoneinfo/zone.tab available, that's what the Wikipedia article is talking about).

Embedded system? I dunno if setting TZ will do any good (and, of course, you've got to have the proper offset and a way to figure out when or if daylight time goes into effect) or you just set your system clock to UTC and be done with it, eh?

Hope this helps some.

Yes. It is very helpful. Thank you very much for the info.