How to change my Luteal phase

Whitney • I`m 29 yrs old and have been married for 7 yrs. We have 3 kids daughter (7) son (5) daughter (1).
I have this app and another <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period app</a> but I know my Luteal phase is not 14 days I usually ovulate late like 18-21 days which makes my Luteal like 10-12 days I've added previous periods but won't change from 14 days