Due date

So I'm due September 10th according to my dr which makes me 25 weeks today & for ships & giggs I googled "im due September 10th how many weeks am I" & it says I'm 25 weeks 4 days and then I downloaded his First Response app & with my due date it says I'm 26 weeks..obviously my dr knows how many weeks I am but darn you Internet for giving me different dates lol I can't even use the First Response app cuz to get the weeks correct it gives me a different due date lol anyone else encounter this weirdness? Lol