Having been in the borg my entire life (now over 40), I never got a good answer to why the Memorial could not be "celebrated" in the afternoon.
Remember, the Jewish "day" runs from sunset to sunset. And 2 out of every 7 years, Nisan 14 falls on a Friday or Saturday. So in many cities where three or more congregations share the same building, they end up renting a building for some of the congregations since generally they can only have two congregations using it in one evening.
My question is, when Nisan 14 falls on a Friday or Saturday, why not have one or more Celebrations the following afternoon, either Saturday or Sunday ??? It would still be Nisan 14. Plus, there wouldn't be such a rush to push everyone out of the building and parking lot to get the next group in.
I have asked this question many times and never got a good answer.
***** Rub a Dub