is third trimester 27 weeks or 29 weeks?

okay cause I'm 28 weeks. But someone said you're not in your third trimester until 29 weeks. But I have an app that tells me I'm already in my 3rd trimester. So I'm confused. lol

@redheadkay, I accidentally deleted your comment trying to reply 🤦🏼‍♀️

@veropetty lol its OK but yes it's 28. I had an app that said 27 but Dr's go by 28 lol

@redheadkay, oh okay nice too know lol