Ok this may sound weird but I know withing 2 hours when I conceived a child.. Im absolutely sure on the date.. It was a Sun (well after midnight) so Monday between 12am and 2am on August 12, 1991..
My due date was May 15th.. I had my daughter on May 12th a little after 4:18Am.. Guess it takes time for those buggers to swim...

LOL
For anyone that wants to study or look at the transits...
I did it synastry style...
I am on the inside, my transits are on the outside.. I picked 1am, the time between 12 and 2..
Also just for the record, the father is a Cap.