So I have 3 period tracking apps, 2 of which are Glow and <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a>. <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> and my other <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> are in sync together and say the same predicted start date of my period. Where <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> and Glow get the exact same information yet glow says I'm going to start this Sunday and <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> says in a week. Why are they so off? Neither of them are usually right.