The Jewish calendar calculates a day from sunset to sunset, thus the Last Supper (on the Thursday evening) and Jesus' crucifixion (on Friday afternoon) *happened in the same day*. In John Gospel this day was the 14th of Nisan (April 3, 33 CE) of the Jewish calendar; In the three Synoptic Gospels the Last Supper is a Passover meal so Jesus' crucifixion must have taken place during the afternoon of the festival itself, the 15th of Nisan (April 4, 33 CE). 

Both dates obviously can not be true. Which date is correct?