Different ovulation dates

Kylie • ❤
I use Glow & period tracker to track my fertility and my period.. I noticed recently though that glow has been giving me a different date (this cycle it's a WEEK later) than period tracker and I'm not sure which to go by? 
I'm a lesbian trying to conceive, so I can't just have sex the entire time to hope to conceive. It has to be concise and planned so it's frustrating. Does anyone else have this issue?