Jesus and his disciples were Jewish men. He chose the Passover time to reveal to his disciples of his death because then they would understand the symbolism and how his sacrifice would free their sins like Moses freed the Israelites.
The gospels mark 14:1-26 represents how Jesus is observing the important aspect of the Passover feast because Jesus told his disciples to go make preparations for the celebration. Later in the feast, Jesus blesses some unleavened bread representing his body (the bread had no yeast like Jesus had no sin) and the wine representing his blood which he then asks the men to