Ovulation date

Blair • In love with my bestfriend & pregnant with #1 EDD: November 16th, 2015.
Glow is telling me that my peak day is today but every other <a href="https://play.google.com/store/apps/details?id=com.glow.android">ovulation calendar</a> is saying my ovulation day is Monday... how do I know which one is correct?