Most Christians worship on Sunday in honor of Christ's resurrection on "Easter Sunday." This, in turn, has led to the assumption that Saturday is the seventh-day Sabbath of the Bible. Jews and many Protestants worship on Saturday based on this belief.
The problem is that the calendar used to find Sunday and Saturday is a counterfeit. The modern Gregorian calendar was devised by a Jesuit astronomer, Christopher Clavius and named for Pope Gregory XIII. It is an adaption of the pagan Julian calendar, designed for Julius Caesar in 45 B.C.E.
The significance of this counterfeit calendar is that the 10 Commandment law commands worship on the seventh day of the week: "Remember the Sabbath day, to keep it holy, Six days you shall labor and do all your work, but the seventh day is the Sabbath." (Exodus 20:8-10) This was not a time-limited statute that was to pass away at the cross. Rather, as part of the divine law, it is binding upon all peoples through all time. "Verily My Sabbaths ye shall keep: for it is a sign between Me and you throughout your generations; that ye may know that I am YHWH that doth sanctify you." (Exodus 31:13)
It is impossible to find the true seventh-day Sabbath using the counterfeit pagan/papal calendar in use today. In order to honor the Creator by keeping holy His Sabbath, it is necessary to use the method of time-keeping He established at Creation.
This calendar was used by patriarchs, prophets, the Saviour and His disciples and all the faithful for hundreds of years after the crucifixion. Unlike the Gregorian calendar, which is a solar calendar, the Biblical calendar is a luni-solar calendar.
During Creation week, the Creator declared: "Let there be lights in the firmament of heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years." (Genesis 1:14) The word "seasons" comes fom the word mo'ed which is the same word used throughout Leviticus 23 to apply to the seventh-day Sabbath and annual religious observances. "Mo'ed is used in a broad sense for all religious assemblies. ... It is a common term for the worshiping assembly of Elohim's people." (#4150, "Lexical Aids to the Old Testament," Hebrew-Greek-English Key Word Study Bible.)
Scripture clearly states that the moon was to be used for calculating mo'ed or religious assemblies: "He appointed the moon for seasons [mo'ed]." (Psalm 104:19)
The luni-solar calendar of Scripture is the only calendar that uses all the lights of the heavens. The pagan/papal Gregorian calendar in civil use around the world uses only the sun. It does not fit the Biblical criteria for being the time-keeping system of the Creator because it uses only one of the lights in the heavens. Also, its continuous weekly cycle is divorced from anything in nature.
The Biblical calendar begins each month at dawn after the conjunction. The first day of each month is New Moon day (see 1 Samuel 20:5, 18 & 24). The New Moon also restarts the weekly cycle. Thus, the seventh day Sabbath always falls on the 8th, 15th, 22nd, and 29th days of the lunar month, following New Moon day. It is impossible to find the first day of the Biblical week (and thus the day of the resurrection) or the seventh-day Sabbath using the modern calendar. only by using the Creator's original method of time-keeping is it possible to find the true seventh-day Sabbath and the real day of the Saviour's resurrection.
"It shall be established forever as the moon, and as a faithful witness in heaven. Selah." (Psalm 89:37)
Neither Sunday nor Saturday is the Biblical Worship Day!