Thanks for your question. Periods always seem to come at the worst times, don't they? I think every woman has been in your situation at some point, myself included.
If your period always lasts 5 days, it's quite possible that your current one will be the same. However, it might even be longer since your skipped the previous one.Unfortunately, there aren't any proven methods for making your period go faster or lighter.
If you're still on your period on Christmas day, I would recommend wearing a tampon and pantyliner, and change them often during the event to prevent leakage.
Good luck and let us know how the event goes!