Thanks, everyone! I know that there are different ways to calculate (and that, really, it's pretty arbitrary to a great extent), but wasn't sure what convention was used here. Seems like that would be a great piece of info to add to the intro page for each trimester message board!
Re: Second Trimester on The Bump
40 weeks / 3 trimesters = 13.33 weeks per trimester.
13.33 x 2 = 26.66 weeks (or roughly 26 weeks 6 days).
Hth!