More often than not, yeah... Seems like most "flowering times" are a couple weeks short. If you count it starting when the flowers begin to show it's usually more accurate, but most folks in the beginning start to count down from the day they flip to 12/12. Happens to us all!
Simplest is to not count. It won’t be ready in nine weeks just wait until it’s done. I never count it’s done when they’re done. now when I clone I know how long but that’s with a strain I’ve cloned and ran several rooms of at least 3 to 4 times. But still don’t count honestly.