Not everyone has two-day Prime, so if you want those holiday gifts to arrive on time, here's when you need to get them in the mail...
Depending on which service you use, FedEx, UPS, USPS, etc, each has their own shipping deadlines. Consumer Reports says you should start placing your orders sooner rather than later, but certainly before Tuesday December 18th, which they reveal is pretty much the very latest if sending out across the US.
You could wait until the last minute, but that will cost you a "premium" price. So to avoid being late, don't procrastinate!