Mailing Deadlines for arrival before Christmas

For my Sweetfire Creations mailings, I like to know when is the last day I can mail something for it to arrive before Christmas.  I found a really good article in the Washington Times about that.   Here is the link:   Know your holiday shipping deadlines for Christmas gift delivery by Dec. 25

I do mostly first class mail and that deadline is December 20th this year.  Please note that it does take a little time to prepare the item for shipping and getting to the post office so try to add a cushion of at least a day to be on the safe side.