Dec. 19 is considered the busiest day of the year for the United States Postal Service, as thousands of Americans rush to send out last-minute holiday cards and gifts.

Postal officials say they expect the office to handle more than 600 million letters and packages on this day, which is 100 million more than the average.

"We have hired additional staff, we have season workers. We're calling a lot of overtime," says Postal Service spokesman George Flood.

Flood says that the Postal Service also expects to handle 14 percent more packages this holiday season, compared to last year. This is likely due to an increase in online shopping.

Those New Jersey residents who still need to mail gifts by Christmas have several options to get their packages delivered on time. Packages will need to be sent by First Class mail by Tuesday, Priority Mail Service by Wednesday and Priority Mail Express by Friday.

Some companies like Amazon are still guaranteeing shipping in time for Christmas on certain orders even if they are placed as late as Christmas Eve.