This is the home page of the ThreeTen project, which provides a date and time API for Java. It originally started as JSR-310 a formal project within the Java Community Process.
As well as information about Java SE 8, the project also provides a backport for Java SE 7 and a jar file of extra classes for Java SE 8.
Main project for Java SE 8
This site holds reference documentation for ThreeTen and JSR-310. This supplements the Javadoc, providing a broader user guide. The documentation is applicable to both the backport and JDK 1.8 - only the package name changes.
Backport for Java SE 7
A backport has been provided for Java SE 7 hosted here at GitHub. The aim of the backport is to allow developers on Java SE 7 to access an API that is very similar to the one in Java SE 8. The backport is NOT an official implementation of JSR-310, as that would involve many complex legal/procedural hoops.
Not every piece of functionality in the domain of date/time ended up in OpenJDK and Java SE 8. The “extras” have been combined into a new project - ThreeTen-Extra - which can be used as an additional date/time jar file on Java SE 8.