I have window dates in two cells. For example:
Where
In cell d1 I have the date: 1/3/2014 7:00
I would like to look up the date in a/b and if d falls between those dates then I would like for it to return the code for the window.
Assuming you have multiple "windows" listed in order with no gaps perhaps try LOOKUP like
=LOOKUP(D1,A1:C10)
see example