With an increase in early and online shopping for gifts, there is no longer a "busiest day" for holiday shipping, but the U.S. Postal Service says there are still some dates you should heed to make sure your packages and letters reach their destination on time.

The Postal Service says its busiest time is now two weeks before Christmas. Starting the week of Dec. 10, customer traffic is expected to increase, and the Postal Service expects to deliver nearly 200 million packages per week during these two weeks.

The week of Dec. 17-23 is predicted to be the busiest mailing, shipping and delivery week, when nearly 3 billion pieces of First-Class Mail, including greeting cards, will be processed and delivered.

The U.S. Postal Service expects to deliver nearly 15 billion pieces of mail and 900 million packages, for a total of nearly 16 billion deliveries between Thanksgiving and New Year's Day.

Once again the Postal Service is expanding its Sunday delivery operations to locations with high package volumes beginning Nov. 25.

The Postal Service already delivers packages on Sundays in most major cities and anticipates delivering more than 8 million packages on Sundays this December. Mail carriers will also deliver packages on Christmas Day in select locations.

The Boardman and Poland Post Offices will be open on Sunday, December 16, 10:00 a.m. to 4:00 p.m.

The Postal Service also processes mail for overseas Department of Defense (DoD) and Department of State (DoS) recipients. Interestingly, the DoD measures their mail volumes in pounds not pieces, and it's expected that the Postal Service will process more than 16 million pounds of mail for DoD and DoS recipients between Thanksgiving and New Year's Eve.

The Postal Service anticipates Dec. 17 will be the Postal Service's busiest day online with more than 8 million consumers predicted to visit usps.com for help shipping holiday packages. It's predicted that nearly 105 million people will visit the postal website between Thanksgiving and New Year's Day.

It's estimated nearly 400,000 consumers will use the Click-N-Ship feature and other online services on Dec. 17 to order free Priority Mail boxes, print shipping labels, purchase postage and request free next-day Package Pickup.

Informed Delivery, the Postal Service's free daily digital preview. lets you manage your packages and sneak a peek at cards headed your way. You can also see some exterior images of magazines and catalogs from your mobile app, dashboard, tablet or computer.

The Postal Service recommends the following mailing and shipping deadlines:

Dec. 4 - APO/FPO/DPO (ZIP Code 093 only) Priority Mail and First-Class Mail

Dec. 11 - APO/FPO/DPO (all other ZIP Codes) Priority Mail and First-Class Mail

Dec. 14 - USPS Retail Ground

Dec. 18 - APO/FPO/DPO (except ZIP Code 093) USPS Priority Mail Express

Dec. 20 - First-Class Mail (including greeting cards)

Dec. 20 - First-class packages (up to 15.99 ounces)

Dec. 20 - Hawaii to mainland Priority Mail and First-Class Mail

Dec. 20 - Priority Mail

Dec. 20 - Alaska to mainland Priority Mail and First-Class Mail

Dec. 22 - Alaska to mainland Priority Mail Express

Dec. 22 - Hawaii to mainland Priority Mail Express

Dec. 22 - Priority Mail Express

Dates are for estimated delivery before December 25. The actual delivery date may vary depending on origin, destination, Post Office acceptance date and time and other conditions. Some restrictions apply.

For Priority Mail Express shipments mailed December 22 through December 25, the money-back guarantee applies only if the shipment was not delivered, or delivery was not attempted, within two (2) business days.

Additional news and information, including all domestic, international and military mailing and shipping deadlines, can be found at the Postal Service Holiday Newsroom at usps.com/holidaynews.