Christmas Time!

If it's beforeThanksgiving, every creature you
control gets -2/-2.
If it's December, every creature gets an ornament counter (They do nothing. They're just decorative.)
If it's the week of Christmas, every creature you control gets +1/+1
If it's December 23 or 24, every creature your opponent fights one creature you control each.
If it's Christmas (December 25), you win the
game.