I know this is a very old thread, but I'm having a similar problem that I can't figure out. In an Access query, I need to display a string representing the 3-character abbreviation of the previous month. I've tried Format(Month(Now())-1,"mmm") and only get "Jan", never the previous month. I have another field in the query where I need to display the long month name and used MonthName(Month(Now())-1), which works correctly.