PhotoIt's happening more every year. Shoppers are making fewer trips to the mall and buying more gifts online.

In the preliminary numbers from Black Friday weekend, we find more evidence of that. Store sales are down, balanced by significant increases in online purchases.

There are many things to take away from that but one important one is this: delivery services are going to be busier than ever this year to handle the crush of packages. That's why it will be important to know what the shipping deadlines are.

You'll find domestic shipping deadlines for December 25 delivery below:

U.S. Postal Service

  • If you want to send via standard parcel post, it has to be mailed by December 15.
  • Using First Class Mail, ship it by December 19.
  • December 21 is the last day to send packages by Priority Mail
  • December 23 is the final day for getting it there using Priority Express Mail

UPS

  • The last day to ship UPS Ground is December 17
  • The last day to ship UPS 3 Day Select is December 18
  • Your last day to ship via UPS 2nd Day Air is December 22
  • December 23 is the last day to ship via UPS Next Day Air
  • December 24 is the last day to ship via UPS Express Critical

FedEx

  • You can ship using FedEx SmartPost up until December 14
  • You can ship usingFedEx Home Delivery and FedEx Ground up until December 16
  • You have until December 21 to ship using FedEx Express Saver
  • December 22 is the deadline for shipping via FedEx 2Day and FedEx 2Day A.M.
  • The last day to ship via FedEx Standard Overnight, FedEx Priority Overnight, and FedEx First Overnight is December 23.
  • Fed Ex says you can even ship December 25 and get FedEx SameDay delivery

A word of caution: the closer you get to a deadline and to Christmas Day, the closer you are probably getting to disappointment. Despite the best of planning and intentions, delivery services may have trouble meeting razor close deadlines if shipments turn out to be much heavier than predicted.

It's happened before. As we reported in 2013, delivery services were swamped with packages and complaints.

And remember, while retailers may promise Christmas miracles when it comes to last minute deliveries -- they aren't making the deliveries. One of the above delivery services is.