John B. Turpish wrote: Thank you.

On Fri, Aug 20, 2010 at 11:23 AM, Christoph Duelli wrote:

...

Code: time_t now = time(NULL); boost::posix_time::ptime pt = boost::posix_time::from_time_t(now); struct tm tm = to_tm(pt); time_t should_be_now = mktime(&tm); BOOST_CHECK_EQUAL(now, should_be_now);

fails for me: now is by 7200 seconds (i.e. 2 hours) ahead of.

Is this a bug in date_time or am I just failing to use it properly?

I am by no means an expert, so take this with a grain of salt. [snip] mktime, on the other hand, assumes the tm represents your local time (http://cplusplus.com/reference/clibrary/ctime/mktime/).

Whether I'm right or wrong should be easily testable, especially for you (since you know

what timezone your PC is set to). Add to your program a few output lines showing members of the tm and see if it looks right for your local time. However, that does not really help, because the struct tm that Boost ptime

Yes, with t = time(0) t == mktime(localtime(t)) but t != mktime(gmtime(t)) produces is different from both gmtime and localtime: DUMP gmtime t.tm_sec=50 t.tm_min=31 t.tm_hour=9 t.tm_mday=23 t.tm_mon=7 t.tm_year=110 t.tm_wday=1 t.tm_yday=234 t.tm_isdst=0 t.tm_gmtoff=0 t.tm_zone=GMT diff(time,mktime(gmtime(time)))=3600 DUMP localtime t.tm_sec=50 t.tm_min=31 t.tm_hour=11 t.tm_mday=23 t.tm_mon=7 t.tm_year=110 t.tm_wday=1 t.tm_yday=234 t.tm_isdst=1 t.tm_gmtoff=7200 t.tm_zone=CEST diff(time,mktime(localtime(time)))=0 DUMP boost from_time_t -> to_tm t.tm_sec=50 t.tm_min=31 t.tm_hour=9 t.tm_mday=23 t.tm_mon=7 t.tm_year=110 t.tm_wday=1 t.tm_yday=234 t.tm_isdst=-1 t.tm_gmtoff=0 t.tm_zone=NULL diff(time,mktime(to_tm(from_time_t(time))))=7200 It is not obvious how to fix the tm obtained from to_tm. Probably it is easier to fix the resulting time_t. I guess I will settle for the approach given in http://lists.boost.org/boost-users/2007/07/29567.php and stop using from_time_t and to_tm Best regards Christoph