The Jewish calendar as we know it was created by the scholar Hillel in about 358 BC.
Just for the sake of clarity, it was AD, not BC. I have a mentor friend, he has a conspiracy theory that Hillel worked for Constantine to subvert the Jews and to hide the real Shabbat.
That friend is a good man. He's a lunar Sabbath observer, which I am not. However, he believes also that the true Sabbath has been hidden from us and will be restored during the Second Coming. His view is that the real Sabbath was lost when the sun was moved backwards on the stairs by Yahweh for Hezekiah.
It's a topic I've been researching but not convinced enough of either direction.
I spent a long time out in the world. I worked in nightclubs and bars for many years. And, during times when I didn't work in those places, I was often in them anyway. I've always been social, and drawn to the center of the "celebration." I like to use the term "revelry."
Instinctually I feel compelled to accept that we have it right with Saturday primarily because Friday nights and Saturdays are THE time that the "world of revelry" parties hard. The majority of the world let's go of the workaday week and seeks oblivion in partying. For many people it is the greatest distraction. That lifestyle feels very much like the Luciferian inversion of the Biblical Sabbath.
I'm willing to accept that we have the wrong day. I don't believe that, but it's a discussion I don't mind. The idea that we can just make up our own minds, however, that idea isn't supported by scripture. It feels Luciferian in nature, the idea that I can create my own sense of what is sin and what isn't sin.
Yahweh rested on the seventh day and sanctified it. Maybe that's Tuesday, or the seventh day of the moon cycle after the not-counted zero day of reset. I have a hard time with the lunar calendar because it isn't every seven days, and they can't even seem to get it right between themselves. We know a lot of lunar people and they're always asking each other what their next month's Sabbath day will be and comparing notes.