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I don't think there is a OVERLAPS() function that you could use. You'll have to stick to the usual test:
WHERE a.StartTime < b.EndTime
AND b.StartTime < a.EndTime
Change < to <=, depending on how you want your Overlap test to function on end cases, when an end time (or date) is exactly the same as the other start time. I guess such behaviour may be wanted for dates.