Footnote

a The modern Jewish calendar determines the beginning of the month of Nisan by the astronomical new moon, but that technique was not used in the first century. Instead, the month began when the new moon was first visible in Jerusalem, which can be a day or more after the moment of the astronomical new moon. This difference is one reason why the date on which Jehovah’s Witnesses observe the Memorial does not always coincide with the date used by modern Jews for the Passover.