PEAR date and time zone classes

Generic PEAR classes for representation and manipulation of dates,
  times and time zones without the need of timestamps, which is a huge
  limitation for php programs. Includes time zone data, time zone
  conversions and many date/time conversions. It does not rely on 32-bit
  system date stamps, so you can display calendars and compare dates that
  date pre 1970 and post 2038. This package also provides a class to
  convert date strings between Gregorian and Human calendar formats.