I wouldn't use composite keys at all ever. In this case, each month gets one field with a number corresponding to its place in the calendar and another field with its generic name (eg 1/January). The number serves as the key, the name as the caption. There are two more fields that identify the month and quarter uniquely within the database (eg 1/January 06; 14/February 07; 27/March 08). Again, the number serves as the key, the name as the name the users see.