Confused..

Amanda • 5 years of love 😍 teacher 👩🏻‍🏫 dog mom 🐾 mommy to Ava 9/5 👶🏼

So I have a few pregnancy apps. nurture, what to expect and pregnancy+ says 6w5d, but Glow and Babycenter says 6w6d.. what the heck? Which one do you guys follow?