Which day of the week is the Biblical Sabbath day? ?

The 7th day Sabbath is saturday.

The biblical Sabbath was determined using a different calendar scheme than the one we use today, where the week reset every new moon, when the new month began. The first day of the month was not a work day; the first workday being the second day, so that the Sabbath fell on the 8th, 15th, 22nd, and 29th of every month. When this calendar is juxtaposed with ours, the Sabbath wanders through our fixed week.

They had just come out of Egypt and having a day of rest was out of the question. But we now know the health benefits of taking a day to rest during the week. We are not under the old laws but they are for our own good. We know the health laws in the bible would keep us from things like the corona virus. Eating pigs gave people worms. Killed more people than it helped. Now we know eating bats are not good idea. But the bible told us that a long time ago. So now we know the original purpose was for humans to eat the vegetation and if we did that we would be healthy just as taking a day to rest during the week would be good for you.

God created everything in 6 day's and rested on the 7th day. That's all the bible say's. At that time the day's wasn't named. Man created the calendar /  named the days of the week.

you know.. you can blow your mind thinking about this.. there are different calenders used all around the world, and they all have different names they use for different days of the week... you never know if Sunday or Saturday or whatever day is actually correct cause of who gave the days their names.. what if they are all mixed up. and Sunday isnt actually Sunday, etc etc.. You could think yourself silly worrying about it.. I feel that if you just choose one day to relax and use as worship. you are good to go

It's typically today, Thursday, in most real religions since that's the actual day that god rested.

It starts with sundown of fridays and ends sundown of saturdays (24 hrs)

The Jews worshiped on Saturday, the Sabbath.  After the Resurrection Christians worshiped on the Lord's Day, Sunday.

That would be Saturday.  Last day of the week, day to rest.

It was Saturday.

It changed. Up until the alleged Resurrection, everyone would have observed it on Saturday. After it, Jews continued to observe it on the same day whilst Christians began to observe it on a Sunday.