you can only get it in Hardmode
Presents drop during the Christmas season in any world, but what comes out of them is decided by the world you open them in, not the world you collected them from. Cracking a pile in a fresh pre-Hardmode save will never produce one of these. Hold the presents until the wall is down.
do not set it off early
Nothing stops you carrying one into a pre-Hardmode world and starting the Frost Legion there, and nothing about the event scales down to meet you. The snowmen hit considerably harder than a goblin invasion and they arrive in numbers. Build an arena and bring Hardmode weapons, or you are just feeding it.
requirement
Your character needs a certain amount of maximum health before the game will accept the item at all. Once you clear that bar it stops checking, so an established character can carry globes anywhere afterward.