Please supply the version of Crystal and database used.
Does your data contain all of these dates, or do you need to fabricate dates?
Is this all that you need, or are you going to be performing some aggregate functions?
You can create a period table for extracting this, use a SQL Expression or Crystal formula that you could then use to filter only datepart(d,table.date) = 2, and there are other ways.
Rather than asking for help with a function, consider describing your data and requirements more fully.
-k