DATETIME, DATE, and TIMESTAMP Types

http://dev.mysql.com/doc/refman/5.0/en/datetime.html

Problems Using DATE Columns ( datetime mysql compare )

http://dev.mysql.com/doc/refman/5.0/en/using-date.html

Date and Time Functions

http://dev.mysql.com/doc/refman/5.0/en/date-and-time-functions.html