A little help from the scholarly types would be appreciated here...
The JW Memorial is on April 9th this year. The Society teaches that Jesus had Passover with his apostles and then the Last Supper (one incident split into two but that's another argument) after sundown Nisan 14. Jesus was then betrayed, tortured and impaled (crucified - whatever) the following day, still Nisan 14th before sundown (which would usher in Nisan 15).
According to the Hebrew calender, Nisan 14th falls on April 8th this year. I'm assuming that Nisan 14th starts at sundown the 8th and goes through April 9th to sundown.
So if Nisan 14 is on the 8th, after sundown, why is the Memorial on the 9th(Nisan 15th) after sundown?