Serial date numbers are in days; entries from the file are in hours. You are taking a base time in days (a good step in itself) and adding hours as if they were days.
There is a trick available here: whenever you populate a datevec or datetime field with a higher value than the normal per-cycle maximum, then the extra is carried up to as many fields above as necessary.
dtime = datetime(1950, 1, 1, time, 0, 0)
Looks like you would get 01-Jan-2011 12:00:00 to 31-Dec-2011 12:00:00
