When you're counting the length of your relationship in months, it's probably not the time to start ring shopping or planning the honeymoon.

But if that relationship belongs to Taylor Swift, then stop the presses!

T-Swift and Calvin Harris have been dating for 15 months now. Scratch that, they dated for 15 months.

The power couple apparently broke up last week and he actually did the dumping. (Will she still find a way to work that into her next album -- you bet!)

A source says things just fizzled out so Calvin decided they should go their separate ways. But Taylor is pretty upset because she stuck by him when he had his car accident last month.

Isn't that what we are just supposed to do for our loved ones?

By the way, the two met back in February of 2015 through fellow musician Elle Goulding. Taylor is 26 while Calvin is 32.