You have not lived until you've had Christmas on a hot summer day. Winter Christmas has nothing on Summer Christmas, seriously. The barbeque, the pools, the fun... it's just so much better. Snow is cool and all, but seriously, it's much more fun when you can go in and outdoors with a whole lot of people around on a nice Christmas day. Wonderful. It's just the whole atmosphere, it's much more relaxed and there's a much more free feeling than there is in the Northern Hemisphere.

EDIT: From what I recall, holidays usually began late November to mid-December (the older you were, the earlier the holidays tended to begin) and went on until the end of January. You would then get three additional sets of holidays throughout the year, each two weeks long.