NTP and time zones

[Raynald Boucher]

Greetings all,

I just had a discussion with a superior about the upcoming necessity to dhange our timezone data on an old Mandrake 8.2 Linux machine.

He claims that we don't have to because the machine clock is maintained by NTP.

I would think the time returned fro the time server is in universal time format which is then interpreted by the client's timezone settings ($TZ for UNIX, /etc/localtime for linux).

Can anyone confirm the process and/or point me to documentation that clearly explains it?

Thank you.

RayB

[Ivan Ferreira · Accepted solution]

You are right. The NTP server provides the time in UTC, and your client timezone dictates when to enter and leave DST.

A good explanation about the whole process is here:

http://tldp.org/HOWTO/TimePrecision-HOWTO/

[James R. Ferguson]

Hi Ray:

You are correct. Show your "superior" the following and see if it doesn't reinforce the notion of a timezone as a +- offset of time *from* universal (Greenwich) time:

# date
# TZ=UTC date
# TZ=EST5EDT date
# TZ=PST8PDT date
# TZ=CST-9:30CDT date

The above set the TZ variable only for the duration of the commandline.

The dates for Standard or Daylight Saving time transitions are coded in configuration files. In the United States, as you aware, the Spring transition will occur three weeks earlier than before and the Fall change a week later than previously. Once again, though, the actual server clock (and, of course the time returned by NTP from its sources) never changes --- only the +- delta value defined for the timezone.

Regards!

...JRF...

[Raynald Boucher]

Thank you,
2 good responses!

Case closed.