IsTime

Reports whether the value of a string is a valid time value.

IsTime ( timevalue )

Argument	Description
timevalue	A string whose value you want to test to determine whether it is a valid time

Boolean. Returns true if timevalue is a valid time and false if it is not.

This expression returns true:

IsTime("8:00:00 am")

This expression returns false:

IsTime("25:00")

To pass this validation rule, the value in start_time must be a time:

IsTime(start_time)