The USPS has posted the deadline dates for those planning to ship in time for holidays. many people can't make it to be with everyone for the holiday season so they end up shipping their gifts. The post office wants to make sure they can get your gift to its destination in time for Christmas morning so they have posted the deadlines well in advance of the rush.

Domestic USPS Mail-By Dates to assure delivery by December 24th

 First-Class Mail  Dec 19
 Priority Mail  Dec 20
 Priority Mail Express  Dec 22

International shipping for the holidays, please use these Mail-By Dates

 International Mail Addressed To  First-Class International  Priority Mail International  Priority Mail Express International
 Africa  Nov 30  Nov 30  Dec  7
 Asia/Pacific Rim  Dec  7  Dec  7  Dec 14
 Australia/New Zealand  Dec  7  Dec  7  Dec 14
 Canada  Dec  7  Dec  9  Dec 16
 Caribbean  Dec  7  Dec  9  Dec 14
 Central & South America  Nov 30  Nov 30  Dec   9
 Mexico  Dec  7  Dec  7  Dec 14
 Europe  Dec  7  Dec  9  Dec 14
 Middle East  Dec  7  Dec  9  Dec 14

Happy Holidays and Happy Shipping!