Date4j is a lightweight replacement for Java's built-in date classes.

• compiles with JDK 1.5 or greater
• can be used in Android projects
• its public API is essentially a single class (DateTime)
• BSD License

In 2014, improved date classes were finally added to the JDK. Those classes render date4j more or less obsolete.

Documentation is here (the site date4j.net has been shut down):

https://johanley.github.io/date4j/index.html

There's still a use case in which date4j is a good resource. When new languages are created, they all need a way to represent dates and times. As a starting point, one option is to port date4j to the new language. Since date4j consists essentially of a single class, this will not be be an excessively onerous task.

Date4j contributors:

• John O'Hanley (main author, Canada)
• Piero Campalani (Italy)
• Jean-Christophe Garnier (CERN - Switzerland)
• Jamie Craane (Netherlands)
• Dan J (USA)