Figuring out when Jesus ate the Last Supper with his disciples and which day he died on the cross is not easy. Why? First of all, Jews started new days each evening! Our days (in the Gregorian calendar) begin and end in the middle of the night and consider daylight the middle of the day. Jewish days began at dusk with the first half of a day being the dark night and the second half of the day being the daylight. That's why Genesis 1 says, "there was evening and morning on day one." That's also why we get confused about the timeline of Jesus' death and resurrection in the Gospels.
If Jesus actually died on Friday afternoon when we celebrate 'Good Friday,' then he would have only been in the grave for 2 nights. But Jesus said he would be in the grave for 3 nights. So either Jesus is wrong (see matthew 12:40), or our holiday is wrong. It's worth investigating.