The price of a stamp will decrease for the first time in nearly a century this Sunday. And the U.S. Postal Service, which was ordered to cut the price by its regulator, is none too happy about it.

USPS said the decline in the price of a postage stamp, from 49 cents to 47 cents, will cost them $2 billion this year. As a result, it will make it even more difficult for them to compete and provide the service its customers demand.

So the USPS is asking for a change in its rate-setting process that could allow them to enact steeper rate hikes in the future.

The last time there was a decrease in the price of postage was back on July 1919, when stamps dropped from 3 cents to 2 cents. On top of that, this is only the third price decrease on record going back to the Civil War.

By the way, the Postal Service isn't funded by tax dollars, so it has to cover the costs of operation through revenue sources such as postage. On top of that, it has reached its borrowing limit.