Third Trimester?

Brittany • 22✌🏻, Cactus living 🌵, Mama to one tiny human with one on the way 👶🏼👦🏼, Air Force Wife.
So question?! FTM here and I always thought that your third trimester starts at 27 weeks but I've read in different places that it's not till you're 28 weeks?! Which one is it? I'll be 27 weeks tomorrow and I was going to make a post about being in my third trimester but I don't want to look like an idiot! Please help!