Hello Andrei If the celebration is annual, or less frequent than annual, I would include the comma before 'due'. The celebration has already been defined temporally (it's the 'next' celebration), so a comma is necessary to separate it from the additional information ('due in 2012'). ' Tricky one, though, and others may disagree!
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.