My moods usually change quickly, between a few minutes to a few hours. I can be sad, happy, irritable, excited, panicky, hyper, depressed, sweet, hateful, and everything in between... all within a day. I have, however, had moods that lasted longer. I've had periods of depression that have gone on for days, including suicidal thinking. And I've had "ups" that have lasted as long as 48 hours.

The longer mood "swings", I believe are actually referred to as mood "states". Longer episodes of certain mood states are typically associated with Bipolar, rather than BPD, but only a doctor would know for sure of course.

I was previously diagnosed bipolar, but one of the red flags that I had been misdiagnosed is that I change moods TOO quickly, even for rapid cycling bipolar. (There were other factors, but that was a big one)