Do not open before christmas

The ribbon on my wrist says do not open before christmas.
Thats what the song says.
But whe you really think about it, when is before christmas, Does it start a few months after it passes?
Or is it until december? then after christmas its no longer before christmas until december comes once more?
So does that mean you cant 'open' your wrist from December 1st to the 25th?

Does this make any sence?
I'm not sure it does