There is no installation needed to use these
functions; they are part of the PHP core.
Note: Getting the latest
The latest version of the timezone database can be
installed via PECL’s » timezonedb.
DateTime support in PHP 5.1.x
Although the DateTime class (and related functions) are enabled
by default since PHP 5.2.0, it is possible to add experimental
support into PHP 5.1.x by using the following flag before