Shoppers using Amazon to buy their Christmas presents will have until Dec. 19 to make their choices and still be guaranteed free shipping in time for the holiday, USA Today reported. The online retail giant extended its deadline, saying that items ordered before 11:59 p.m. ET that day will be delivered by Christmas Eve. Last year, the cutoff date was Dec. 17.

Subscribers to the $99 "Amazon Prime" service, meanwhile, can shop as late as Dec. 22 because their membership includes free 2-day shipping. For a $2.99 fee, they can push it to Dec. 23 for one-day delivery, and for $5.99 per shipment, same-day delivery is available in 12 markets for those who buy by 10 a.m. local time on Christmas Eve, The Associated Press reports.

Amazon expects that Thursday, Dec. 18, will be its busiest shipping day of the year. The online comany's extension announcement follows a promise made by competitor Wal-Mart, who last week said it will still guarantee Christmas Eve delivery for items sent by standard shipping and ordered by Dec. 19.

"[Amazon's extension] is possible because of ([ts] growing network of fulfillment and sorting centers [and] ongoing relationship with carriers such as UPS, FedEx and the U.S. Postal Service," Amazon said.

The carriers themselves, however, are taking a more subdued stance when it comes to guarantees for standard service.

FedEx and UPS do not make promises with respect to the timeliness of ground packages leading up to Christmas, MarketWatch said. In fact, both companies last week announced they would suspend money-back guarantees for ground delivery until after Christmas. It's a common move as it allows shippers to focus on their express services.

Given that "last year was something of a nightmare for ... delivery companies," as Consumer Affairs put it, the companies have issued firm guidelines on when individuals should ship their Christmas packages this year to avoid disappointments under the tree, but corporate clients get more flexible deadlines, and they also help couriers by pre-sorting their mail.