Lord’s Supper occurs on the eve before the fourteenth day …

Comment on The Sabbath’s relevance to the debate about origins by Lawrence Calahan.

Lord’s Supper occurs on the eve before the fourteenth day of the month (full moon) following the spring equinox, the 14th of Abib (a word meaning spring) or Nissan 14, as the month is called. This is the day that Jesus was said to have been crucified, just before the Passover, which occurred, and always occurs, on the fourteenth day of the month, the Passover Sabbath. This then means that Jesus was crucified on the 13th, the day before the Sabbath, but this cannot be the case if he ate the Passover supper which occurs on the evening at sunset while the full moon is rising! The reason for this discrepancy is that there are two days of Sabbath at this time, and he rested through both of them, and rose on the third day, just as the scriptures predicted he would! There is the Passover Sabbath and the beginning of the Feast of unleavened bread; which immediately follows the Passover. If I am wrong about this please send me an email and tell me so.

At that time in history Friday was the seventh day of the Roman week, (Saturn was the first planet, Saturday the first day) but the Jews did not recognize nor reverence the days of the Roman week.

Mark 16:2 And very early in the morning the first of the week, they came unto the sepulcher at the rising of the sun.
The first of the week began not on Sunday but on whatever day followed the Sabbaths. Then there came another six days to labor to do all the work necessary to prepare for the final Sabbath day of the month. On the eve of the 21st day of the month the final Sabbath began, and continued through the 22nd until evening. This was an evening of reflection and thanksgiving for all that the Lord has done the previous three Sabbaths. This is a day for counting your blessings. On the first day following this last Sabbath, the first day of the last week of the month, the tithes are calculated and offerings for the poor are laid aside. On this Sabbath eve the half moon rises at midnight, this time it is on its wane, this is the last quarter before another new moon, or new month. The week following is another new moon, which heralds a new month and a new Sabbath cycle.
The Jewish Sabbath is a monthly event beginning at the New Moon and is celebrated every seventh-day, regardless of what day of the week it is on the Roman calendar. It is true that they did not accept nor use the Roman calendar until required by the Romans. This has been the custom since the fifteenth day (full moon) of the second month after leaving Egypt in the wilderness of Sin. (Wilderness of the Moon) Sinai (Mountain of the moon)
Yes it is a true fact of history that they observed their Sabbaths according to the changing of the moon–the bible says so, and so does EGW.

Here is a day given, and the Lord declares it shall be observe throughout your generations “for a perpetual covenant” (Exodus. 31:16), as a sign of obedience and loyalty to God, and yet it is so obscured no one can tell when it comes! Oh, what fallacies men will resort to in order to carry out False theories. The Lord pronounced His blessing upon all who keep holy the Sabbath day. His commandments are given to a thousand generations, and when that period is ended the redeemed host shall be in the city of God and observe the Sabbath there, and especially come up to worship God from Sabbath to Sabbath and from one new moon to another. —MANUSCRIPT 173, 1897,PP 4-5 (DIARY OF ELLEN G. WHITE, JUNE 1897