Is the <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> reliable ? Does it accurately predict your period? I've tried several such as clue, <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> and <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a>......