DateTime::TimeZone is a Perl module framework providing an interface to the
 Olson time zone database. It exposes the database as a set of modules, one
 for each time zone defined, allowing for various optimizations in doing time
 zone calculations.
 .
 The Olson time zone database is the best available source for worldwide time
 zone information and is available from <URL:ftp://ftp.iana.org/tz/releases/>.