Procrastinating on your Christmas cards and holiday gifts? So are millions of other people.
According to the U.S. Postal Service, December 20 is the busiest mailing day of the year, with over 800 million cards and letters expected to be processed.
The previous day, December 19, is the busiest day for package delivery.
Those who haven't even begun sending packages out have a grace period through December 21. USPS says first-class mail and priority mail sent by that day will arrive to its recipient in time for Christmas.
USPS is also offering a money-back guarantee for Christmas Day delivery, for those using Express Mail. This offer is only within certain zip codes; click here or contact your local post office for more details.