Re: [Boost-users] Date-Time question on seconds since epoch

From: Caleb Epstein (caleb.epstein_at_[hidden])
Date: 2005-01-11 09:22:06

On Tue, 11 Jan 2005 07:26:20 -0600, Bill Lear <rael_at_[hidden]> wrote:
> I'd like to determine the total number of seconds between a date and
> the epoch ('00:00:00 1970-01-01 UTC'), The date can be in a timezone
> that has daylight savings.  The date should be converted to UTC, with
> appropriate daylight savings adjustments made, and then the epoch
> subtracted from it.  This should mirror the unix GNU 'date' utility,
> which can be run as:
> 
> % TZ="America/New_York" date --date='2004-10-04 12:14:32' +%s
> 1096906472
> 
> I've looked at the doc, but it's not clear how to do this.  Could
> someone give me a few pointers, please?

I would make use of the standard library facilities timelocal or
timegm to convert a struct tm to time_t format.  The former assumes
the time is expressed in local time (as specified by the TZ
environment variable or via tzset) and the latter assumes it is in
GMT.

The support for timezone conversions in Boost.DateTime is rudimentary
at best and does not currently make use of operating system facilities
like the zoneinfo database.

-- 
Caleb Epstein
caleb dot epstein at gmail dot com