Our LORD is not the author of confusion, so lets lay the proper foundation. This Passover was instructed by our LORD - to - Moses: a Hebrew, of the Tribe of Levi[One of the 12]. Our LORD is "The High-Priest; after the order of Melchizedek" - forever!
The first Passover with Moses was at the beginning of the year: The first Solar-Spring-Equinox, then 15 Days out; beginning at sundown on the 14th. Day. Obedience, and strict attention to details were required: their lives, and a Right-standing-relationship hung in the balance[Ex.12].
"It is the LORD's Passover" Ex.12:11. Revelation via the Holy-Spirit shows that Immanuel-Christ-Jesus, and the LORD in Exodus are the SAME. The Passover Blood continues to the LORD's Supper where bread[Body] and wine[Blood] was eaten and drank as an Additional Covenant: "This do, in remembrance of ME."
The Passover Feast [Ex.12:14] is to be kept "throughout your generations[Levi/Priest]; ye shall keep it a Feast by an Ordinance - forever."
What was nailed to the Cross of Christ = Blood Ordinances/Sacrifices. The term- Last Supper - is Progressive, in New-age-Bibles that practice Easter; which is Pagan. Started by our Enemy, the Thief. We are to practice the Passover Feast every year.
"This do, in remembrance of ME" Luke22:19, 1Cor.11:24. This is a Commandment: a Law.
The question from the Thief for 2016 is: "should Christians be celebrating the Passover."
We should practice the LORD's Passover. "If you love ME, keep MY Commandments" [John14:15].