I have the follwing situation:

Fall semester:
if the account start date (Acctstrt) is equal to or greater than
09/01/2008 and the account stop date (Acctstop) is less than or equal to
01/15/2009 than = Fall

Spring semester:
If (Acctstrt) date greater than or equal to 1/15/2009 and an Acctstop date
of 5/31/09.
= Spring

Summer semester:
if (Acctstrt) 06/01/2009 and the (Acctstop) 8/31/2009.
= Summer