HOW TO SET Embedded Linux /etc/TZ

Why does localtime() return times in UTC even when I have my timezone set?

The uClibc time functions get timezone information from the TZ environment variable, as described in the Single Unix Specification Version 3. See for details on valid settings of TZ. For some additional examples, read in the uClibc mailing list archive. You can store the value of TZ in the file '/etc/TZ' and uClibc will then automagically use the specified setting.

You need to be sure the TZ environment variable is set properly,

since uClibc does not support /etc/zoneinfo junk.

See 'man 3 tzset' or read the SuSv3 docs at

  

for details on how to set TZ for localtime.

For example, here is date with glibc:

    $ date

    Thu Aug  1 14:31:58 MDT 2002

Here is date with uClibc, when the TZ environment variable is set:

    $ TZ=MDT6 ./busybox date

    Thu Aug  1 14:34:53 MDT 2002

This means that MST (Mountain Daylight Time) is 6 hours earlier

than Coordinated Universal Time (UTC) and does not have daylight

saving time.

Here is another simple example:

    $ TZ=JST-9 ./busybox date

    Fri Aug  2 05:40:45 JST 2002

This means that Japanese Standard Time (JST) is 9 hours earlier

than Coordinated Universal Time (UTC) and does not have daylight

saving time.

Here is a more complex example:

    $ TZ=MST7MDT ./busybox date

    Thu Aug  1 14:32:04 MDT 2002

This means that Mountain Standard Time (MST) is 7 hours earlier

than Coordinated Universal Time (UTC).  Both standard time and

daylight saving time apply to this locale.  By default Mountain

Daylight Time (MDT) is one hour ahead of MST.  Since it isn't

otherwise specified, daylight saving time starts on the first

Sunday of April at 2:00 A.M. and ends on the last Sunday of

October at 2:00 A.M.

Here is an even uglier example:

    $ TZ=NST3:30NDT1:30 ./busybox date

    Thu Aug  1 19:13:03 NDT 2002

This means that Newfoundland Standard Time (NST) is 3.5 hours

earlier than Coordinated Universal Time (UTC).  Both standard

time and daylight saving time apply to this locale.  Newfoundland

Daylight Time is 1.5 hours earlier than Coordinated Universal

Time (UTC).

 

Normally, one would set TZ in /etc/profile.

TEST ON MY DEVICE

# cat /etc/TZ 

CST-8

# busybox | head -1

BusyBox v1.19.2 (2011-12-10 10:19:37 CST) multi-call binary.

echo `date` > /tmp/test

echo `date -u` >> /tmp/test

echo `date +%m:%d:%H` >> /tmp/test

# cat /tmp/test 

Sat Jun 2 09:48:13  CST  2012

Sat Jun 2 09:48:13 UTC 2012

06:02:17