Joda Time - Java date and time API - Home: "Joda-Time provides a quality replacement for the Java date and time classes. The design allows for multiple calendar systems, while still providing a simple API. The 'default' calendar is the ISO8601 standard which is used by XML. The Gregorian, Julian, Buddhist and Coptic systems are also included, and we welcome further additions. Supporting classes include time zone, duration, format and parsing."
Production-ready release 1.0 with Apache License 2.0 has just been released!