boost local_date_time CET to UTC - c++

Question

I try to convert a boost local_date_time to UTC but I'm confused about the returned time of utc_time(). Here is a simplified code :
#include "boost/date_time/local_time/local_time.hpp"
int main()
{
using namespace boost::gregorian;
using namespace boost::local_time;
using namespace boost::posix_time;
ptime dt = ptime(date(2015, Mar, 2), hours(0));
time_zone_ptr tz_cet(new boost::local_time::posix_time_zone("CET"));
local_date_time local_dt = boost::local_time::local_date_time(dt, tz_cet);
std::cout << local_dt << std::endl;
std::cout << local_dt.utc_time() << std::endl;
time_zone_ptr tz_utc(new boost::local_time::posix_time_zone("UTC"));
std::cout << local_dt.local_time_in(tz_utc) << std::endl;
}
output:
2015-Mar-02 00:00:00 CET
2015-Mar-02 00:00:00
2015-Mar-02 00:00:00 UTC
UTC should be 1 hour behind CET (Central European Time).
Is this a bug or am I missing something?

Answer 1

The boost::local_time::posix_time_zone("CET") constructor call creates a zone with the CET abbreviation and missing information about offset from UTC, time shift for DST, etc, i.e. the calls boost::local_time::posix_time_zone("CET") and boost::local_time::posix_time_zone("UTC") are different only in the TZ abbreviation names, the rest is the same. The coliru code demonstrates it. The base_utc_offset method calls of the both TZs return 00:00:00.
To fix the issue is necessary either to set time parameters of the CET zone, something like, "CET+01:00:00" or to use the tz_database class to load the timezones from a CSV file.
The following code is the original modified code demonstrating how to fix the problem. Please note that the CET time zone description is not complete and provided only as an example.
#include "boost/date_time/local_time/local_time.hpp"
#include <iostream>
int main()
{
using namespace boost::gregorian;
using namespace boost::local_time;
using namespace boost::posix_time;
ptime dt = ptime(date(2015, Mar, 2), hours(0));
time_zone_ptr tz_cet(new boost::local_time::posix_time_zone("CET+01:00:00"));
local_date_time local_dt = boost::local_time::local_date_time(dt, tz_cet);
std::cout << local_dt << std::endl;
std::cout << local_dt.utc_time() << std::endl;
time_zone_ptr tz_utc(new boost::local_time::posix_time_zone("UTC"));
std::cout << local_dt.local_time_in(tz_utc) << std::endl;
}
The same code on coliru is available by this link.