JodaTime

Free, open-source Java library for working with dates and times

Supported Concepts
Instant
 “An instant in the datetime continuum specified as a number of milliseconds from 1970-01-01T00:00Z”
  Within Joda-Time an instant is represented by the ReadableInstant interface.
  There are four implementations of the interface provided.

 Instant - A simple immutable implementation which is restricted to the UTC time zone and is intended for   time zone and calendar neutral data transfer
 DateTime - The most commonly used class in the library, and an immutable representation of a date and time with calendar and time zone
 DateMidnight - Similar to DateTime and also immutable but with the time component forced to be midnight (at the start of a day)
 MutableDateTime - A mutable representation of date and time with calendar and time zone.

• Partial
 a partial date/time representation (subset of fields) with no time zone
• Interval
 “an interval of time from one millisecond instant to another”
• Duration
 “a duration of time measured in milliseconds”
• Period
 “a period of time defined in terms of fields, for example, 3 years 5 months 2 days and 7 hours”
• Chronology “a pluggable calendar system