I had to add
DateTime::TimeZone::Alias->set( MSK => 'Europe/Moscow' );
to the code cause MSK is not recognized by DateTime::TimeZone module be dafault.
More stuff to research:
- list of timezones – http://www.worldtimezone.com/wtz-names/timezonenames.html
- list of available Perl modules: http://datetime.perl.org/?Modules