Snowballs battle usually starts one week before Christmas, and lasts untill 25th of december in the morning (French time so be carefull !). You should have to collect snowballs by clicking on the banner (each 15 minutes) and throw these snowballs on other players. Each time you will hit a player with a snowball, this player will receive a gift and you will earn a point. These points will be used to unlock paladins and items of snowballs battle's quest. Gifts will become openable on 25th in the morning, when the quest will be over !
This being said, we are not completely safe of a surprise from our admins ! A lot of things can be changed !