Re: [Boost-users] [date_time] timezone bug for boost::posix_time::microsec_clock::local_time()

From: Jeff Garland (jeff_at_[hidden])
Date: 2005-08-20 12:09:47

On Wed, 17 Aug 2005 12:56:16 +1000, Brendon Costa wrote
> Hi,
>
>     I have noticed that there seems to be a problem with the boost 
> date_time library 1.33 (Downloaded about 2 days ago) when trying to 
> use the localtime information under a NetBSD system. Specifically 
> when I have a small test program:
> 
> #include "boost/date_time/posix_time/posix_time.hpp"
> #include "boost/date_time/c_local_time_adjustor.hpp"
> 
> #include <iostream>
> 
> int
> main()
> {
>    using namespace boost::posix_time;
> 
>    ptime loc = microsec_clock::local_time();
>    ptime utc = microsec_clock::universal_time();
>    std::cout << "Local:       " << to_simple_string(loc) << 
> std::endl;   std::cout << "UTC:         " << to_simple_string(utc) 
> << std::endl;
>   
>    std::cout << "Local again: "
>       << to_simple_string(
>          boost::date_time::c_local_adjustor<ptime>::utc_to_local(utc)
> )      << std::endl;   return 0; }
> 
> It will display the same time for both UTC time and Local time 
> (Living in Melbourn Australia) where I expected them to differ.

Hi Brendan -

All of the 'clock' calls depend on the operating system time zone setup to
perform the utc/local conversion.  So I suspect something about your system
setup is requiring you to call tzset() to initialize the environment for
localtime() and gmtime() to work correctly.  Not sure why that would be.  I
presume after tmset() is called once it never needs to be called again?

BTW, in 1.33 there's better support for local time than the old
c_local_adjustor. You might have a look at the tz database functions that
allow you to do adjusment via regions:
  
 tz_database tz_db;
 //data file in lib/date_time/data
 tz_db.load_from_file("date_time_zonespec.csv");
 time_zone_ptr mb_tz = tz_db.time_zone_from_region("Australia/Melbourne");
 
The returned timezone has string names for the timezone, utc offsets, and
daylight savings rules built in.

Jeff