Holiday shipping deadlines for the U.S. Postal Service are quickly approaching. The USPS recommends that if you want a package to be delivered before December 25th in the contiguous United States then you’ll want to have them sent soon. The deadline for USPS Ground Advantage Service and First-Class Mail is Wednesday, December 18th. The deadline for Priority Mail is Thursday, December 19th. And the deadline for Priority Mail Express Service is Saturday, December 21st. The deadline for Priority Mail Express for Military Mail is Monday, December 16th.