Installation
 There is no installation needed to use these
functions; they are part of the PHP core.
 Note: 
  Getting the latest timezone database
  
   The latest version of the timezone database can be installed via PECL's
   » timezonedb.
  
 
 Note: 
  Experimental 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 configure/compile:
   CFLAGS=-DEXPERIMENTAL_DATE_SUPPORT=1