Pill problems

Livie

So I finished my pill pack on my last period and forgot to get a new pack, and now I’m due on my period on the 31st December. I’ve now got new pills, but if I start taking them now (21 dec) will it postpone my period? Or will I still get my period ? Because I don’t want to be on for New Years :( I hope someone can get back to me ASAP xxx