Re: [boost] [datetime] IANA Time Zone Database

Subject: Re: [boost] [datetime] IANA Time Zone Database
From: Maxim Yegorushkin (maxim.yegorushkin_at_[hidden])
Date: 2012-11-08 12:36:07

On 08/11/12 15:15, Artyom Beilis wrote:
> You can use Boost.Locale that is compiled with ICU backend.
>
> ICU supports Time Zone database and you can specify the timezone by its name, parse time or create
>
> date_time object and get POSIX (UTC) time form it.
>
>
> Artyom Beilis
> --------------
> CppCMS - C++ Web Framework:   http://cppcms.com/
> CppDB - C++ SQL Connectivity: http://cppcms.com/sql/cppdb/
>> ________________________________
>> From: Maxim Yegorushkin <maxim.yegorushkin_at_[hidden]>
>> To: boost_at_[hidden]
>> Sent: Thursday, November 8, 2012 4:53 PM
>> Subject: [boost] [datetime] IANA Time Zone Database
>>
>> Hi Boost,
>>
>> I have files with timestamps in various timezones. I would like to be able to convert these timestamps, no matter what timezone they are in (I know the names of the timezones) to UTC timestamps.
>>
>> I looked through datatime library documentation and found date_time_zonespec.csv database which doesn't seem to support the notion of different rules for the same timezone depending on the date. For example, Russia used to have summer time but not any more. Another method seems to be passing a timezone specification string manually, which requires the user to figure what it should be for a particular date.
>>
>> In other words, given a timestamp and its timezone, I would like to be able to convert that timestamp into a UTC timestamp using conversion rules in force at that particular date in the past. Ideally, this would use IANA Time Zone Database or something similar. Is there a facility in boost to do just that?

Oh, thanks Artyom.

That is quite a surprising place to find this functionality. Not sure 
why it is not in datetime library.

Anyway, I managed to get a small test working:

     #include <iostream>
     #include <sstream>
     #include <boost/locale.hpp>

     int main() {
         boost::locale::generator gen;
         std::locale::global(gen("en_GB.UTF-8"));
         std::cout.imbue(std::locale());

         boost::locale::date_time d;
         std::istringstream ss("8 Nov 2012 17:00:00");
         ss >> boost::locale::as::time_zone("America/New_York") >> d;

         std::cout << boost::locale::as::time_zone("UTC") << d << '\n';
         // prints 8 Nov 2012 22:00:00
     }

Thanks a lot!

-- Maxim