As most people are painfully aware of by now, the Java API for handling calendar dates (specifically the classes java.util.Date and java.util.Calendar
java.util.Date
java.util.Calendar
You might find the following post interesting. It pretty much explains how the Calendar class got into the Java API in the first place, and sheds some light on the origins of the date class.
The Seven Habits of Highly Dysfunctional Design