erlang datetime to erlang now

Function to convert erlang datetime to erlang now(), used to mochijson2.

datetime_to_now(DateTime) ->
 	BaseDate = calendar:datetime_to_gregorian_seconds({{1970,1,1},{0,0,0}}) * 1000000,
 	MicroSeconds = calendar:datetime_to_gregorian_seconds(DateTime) * 1000000,
	ErlangSystemTime = MicroSeconds - BaseDate,
	MegaSecs = ErlangSystemTime div 1000000000000, 
	Secs = ErlangSystemTime div 1000000 - MegaSecs * 1000000,
	MicroSecs = ErlangSystemTime rem 1000000,
	{MegaSecs, Secs, MicroSecs}.