Syntax:
TIMESTAMP(expr), TIMESTAMP(expr1,expr2)

With a single argument, this function returns the date or datetime
expression expr as a datetime value. With two arguments, it adds the
time expression expr2 to the date or datetime expression expr1 and
returns the result as a datetime value.

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

