Q. On what day of the week was the Last Supper?
A. The Synoptic Gospels (Matthew, Mark, and Luke) tell us Jesus celebrated the Passover before He was arrested and condemned. The Fourth Gospel (John) informs us Jesus was crucified before the Passover began. Several theories explain this seeming discrepancy. Here’s the theory most convincing to me.
The Jews of Jesus’ time were divided on many issues, especially with regard to the liturgical calendar. The Sadducees and the priests in charge of the temple followed a lunar calendar of 354 days. That calendar set the date of the Jewish festivals according to lunar cycles. Thus Passover was celebrated on a different weekday (of the solar calendar) each year.
However, the Essenes, a Jewish sect of Jesus’ time, followed a 364-day solar calendar, with the festivals always occurring on the same day of the week. The Jews who followed the Essene calendar always observed the Passover on Tuesday night (which for them was the start of Wednesday). <