Ovulation Kit vs Glow App

So apparently the <a href="https://play.google.com/store/apps/details?id=com.glow.android">Glow App</a> and the Ovulation kit I’m using say im ovulating at 2 different times. <a href="https://play.google.com/store/apps/details?id=com.glow.android">Glow app</a> says I ovulate the first week of the month while the ovulation kit says the second week. Has this happen to anyone??