That’s funny; I’ve thought of doing the exact same thing. I’ll also add, “That’s where you were frozen in suspended animation for eight months. Need a sweater?”
Of course, the building will probably be torn down eventually and replaced with a Domino’s Pizza.
Charting. Know the exact date for both of them.
Our two boys were planned and the date of conception could be narrowed down to periods of “trying”. Well, there was this one time that, post-pill, but pre-vasectomy, I became rather involved in the moment and decided to damn the torpedos…
Our daughter is 5 now, and I couldn’t be happier to have been so careless! 
Oh lord! Now I have to tell my son he was conceived while watching Terminator 3 at the movie theater. How classy.
We know with him because of charting and noting times. It was July Third, We had the day off and tarried awhile in bed that morning and then went to an afternoon movie. His sister, any number of times in a 2 week period as we were not keeping track then.
Mr. W and I were married on October 4th, and concieved around the beginning of December.
As we were newlyweds (and still are, I suppose) we really can’t pin it down much closer than that. I don’t even think we could narrow down a time of day…
I’m pretty sure I can for both. The youngest I know for sure since it was the only time that month. The oldest I have a good idea as it was the same time my mother died. We were going to start trying to have a baby, she went off the pill two weeks before hand or so and we didn’t expect anything to happen so quick. I remember saying something to my wife about her being pregnant at the time, turns out she was.
We were trying for all of ours, so there would have been two or maybe three attempts that were possible for each.
Another one using a chart here, although we can’t be 100% of the actual due date (lots of sex that fertile week). We aren’t exactly sure when I ovulated, but obviously were close enough. We can estimate, but not be absolute. I have it in my head I know exactly which time for both of my boys, though; like belladonna, there are very specific moment memories on the likely dates.
First one I was charting so I know the exact date. I kept the chart!
Second one was while we were at my parent’s house for a 2 week visit and we know that we only had sex that one time (what can I say - I’m inhibited).