For ladies who have had IUI

Rayna • Fri, Sep 19 2014 • 38 years old and been blessed with our baby boy born 11/25/15 through IVF and countless prayers.

I am wondering how you calculate where you are in DPO? What do you consider your ovulation date? 36 hours after a trigger shot? Date of the IUI? Day of positive OPK? Day before BBT rise? Sorry, I am just a bit confused.