I agree with Andreas that this is probably easiest to do with Xpath. Also fastest. You can also try with the special Xpath functions MonthFromDate and YearFromDate
e.g. to get all data for december
//Logging.Log[month-from-dateTime(DateAttribute) = 12]
Easier than using filter might be to only retrieve the needed objects from database. If you only want to see objects from a specific month, you can create two date variables, a start date and an end date. In your xpath you can now only retrieve objects where the timestamp is greater than your startdate and smaller than your end date.