Anybody else notice this?

Kinsey • FTM/SAHM to an amazing baby boy! 💙
Do any of you mommies use the What to Expect app? I don't use it much now that I found <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">Nurture</a>, but the baby sizes are so different? Why is this do you think? And which is accurate? (It says 1/18 because <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">Nurture</a> counts Monday as the new week, What to Expect counts Sunday as the new week)