Its 36 hrs before your IUI. My first doctor told me 38 I didn't listen to him and did 36.5 hrs and Had of my two 16mm become my bueatiful baby girl. This time I switched doctors and did 36 hrs. I felt it release my 17mm just 24 min before the 36 hr mark. Yes I am one of the crazies that can feel it reales That just adds to my frustration of getting prego. I know it's not the timing.
So I did 9pm last Friday and released just before 9am on Sunday.
Hope that helps. Good luck
so 10:45pm tonight is when I would do it.