>>What part is undocumented? CTOT, HOUR, and MINUTE are all documented. Maybe I'm missing something . . .
>
>Passing a time, with no date part to the CTOT function and getting back 12/30/1899 plus your time.
>
>Any other non-valid datetime entry returns and empty datetime, but passing just the time, magically gives you a valid date of 12/30/1899...I don't see that documented anywhere

Yeah, I did notice that 1899 date and wondered why it wasn't empty. Doesn't SQL Server use that same date (or maybe 12/31/1899) as the empty date?