The congregations of Jehovah’s Witnesses will be commemorating the memorial of Christ’s death after sundown on April 3 of this year.
This year there is a solar eclipse marking the new moon closest to the Spring Equinox, which starts the month of Nisan. (I am told that Nisan is the name given the month by the Babylonians who were the great astronomers of their day.) This eclipse will be visible in Jerusalem around noon on March 20. Counting 14 days from sundown on March 20 (Nisan 1) takes us to sundown on April 2, or the time when Nisan 14 starts.
The Bible gives no hard rule that the Lord’s Evening Meal must be commemorated on a particular date and time, only that it must be done; for as often as it is done, we proclaim the death of the Lord until his return. (1Co 11:26)
Some commemorate the Last Supper more than once a year. Others hold to an annual celebration only. Whichever view one might subscribe to, no fault can be found with those striving to determine the most accurate date that would correspond to the actual anniversary of the event, the time when the lamb was slaughtered “between the two evenings”, the time between sundown and civil twilight on Nisan 14 (April 2 this year).