Some very useful functions in Excel, particularly when reporting on transactional data, are the following date functions:
Year( ), Month( ) and Day( )
For each of these functions, you need only put the cell reference of a date field between the brackets and it returns the year, month (1-12) or day (1-31).
Using Year( ) and Month( ) in particular, you can add additional columns alongside a list of sales or other transactions to strip the year and month from the date column. This allows you to report by these in a pivot table or a simple Autofilter.