DATESERIAL has two forms. The first form takes three arguments: a year value, a month value, and a day value. It returns a timestamp for the date corresponding to the specified year, month, and day with the time set to 00:00:00.0:
The second form of DATESERIAL takes six arguments: values for the year, month, day, hour, minute, and second. It returns the timestamp for the specified values:
Timestamp DATESERIAL( year Integer, month Integer, day Integer, hour Integer, minute Integer, second Integer )