Nested SQL function calls on related field with DataMapper?

[eluser]Dracos[/eluser]
Workaround: I've gotten around this by wrapping the date_format, convert_tz, from_unixtime calls in a stored function. But I'm sure lots of people would like to know the more direct DM solution.

I added two somewhat related stored functions a couple weeks ago, what's three more for this? Three because in various places I need the entire formatted date, and in others I just need the date or time portions.