>How do I clear a date field and a datetime field

Mechanically, you can do it like this if it's in a table or cursor:

SCATTER NAME xyz BLANK
REPLACE dDate     WITH xyz.dDate
REPLACE tDateTime WITH xyz.tDateTime
RELEASE xyz

Or you can use the blank forms directly:

thisForm.myDateControl.Value     = CTOD("  /  /    ")
thisForm.myDatetimeControl.Value = CTOT("  /  /     :  :   AM")
REPLACE dDate     WITH CTOD("  /  /    ")
REPLACE tDateTime WITH CTOT("  /  /     :  :   AM")

You can also use the BLANK command if it's in a table:

BLANK dDate, tDateTime

And if you need it set back to NULL, you can use:

REPLACE dDate     WITH {  /  /  }
REPLACE tDateTime WITH {  /  /     :  :   AM}