so my last period started 20th september and my cycles are usually 24 days long, every <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">due date calculator</a> seems to say different! this app and ovia say I'm 4 weeks 4 days but a couple of others say 5 weeks because my cycle length is shorter. I'm confused! How can I be 5 weeks? when it's only been 4 since my last period?