Now you have opened up the proverbial can of worms, (the never-ending debate over what day this actually is). Your statement is not even in agreement with the passage you quoted from Mark. Here it is in full:
Mark 14:12-22 KJV
12. And the first day of unleavened bread, when they killed the passover, his disciples said unto him, Where wilt thou that we go and prepare that thou mayest eat the passover?
13. And he sendeth forth two of his disciples, and saith unto them, Go ye into the city, and there shall meet you a man bearing a pitcher of water: follow him.
14. And wheresoever he shall go in, say ye to the goodman of the house, The Master saith, Where is the guestchamber, where I shall eat the passover with my disciples?
15. And he will shew you a large upper room furnished and prepared: there make ready for us.
16. And his disciples went forth, and came into the city, and found as he had said unto them: and they made ready the passover.
17. And in the evening he cometh with the twelve.
18. And as they sat and did eat, Jesus said, Verily I say unto you, One of you which eateth with me shall betray me.
19. And they began to be sorrowful, and to say unto him one by one, Is it I? and another said, Is it I?
20. And he answered and said unto them, It is one of the twelve, that dippeth with me in the dish.
21. The Son of man indeed goeth, as it is written of him: but woe to that man by whom the Son of man is betrayed! good were it for that man if he had never been born.
22. And as they did eat, Jesus took bread, and blessed, and brake it, and gave to them, and said, Take, eat: this is my body.
According to this rendering, (which may or may not be correct) it is the first day of Unleavened Bread and yet further that day, when EVENING comes, then Yeshua sits down with the twelve for the Seder, (and again there is no mention of lamb but only the bread and wine of Melki-Tzedek). :chuckle: