Want to pay ground rates to ship holiday gifts? Today is USPS and FedEx deadline

Want to get your holiday gifts to their destination by December 25 and pay the standard ground shipping rates? Better do it today, because December 15 is the deadline for both FedEx and the U.S. Postal Service.

This is the USPS's busiest week of the season, according to a recent statement from the postal service. Roughly 2.3 billion packages, greeting cards and other pieces of mail will be delivered this week alone, the USPS said. 

That's a big hunk of the more than 12 billion letters, cards and packages the postal service expects to deliver between Thanksgiving and New Year's Day.