Actually, we can be positive that our seventh day is the same day Jesus observed when He was here on Earth - the day He kept every week as the Sabbath. (See Luke 4:16.) The days of the week have never been confused. Here's why some people ask this question ...
Before 1582, the world went by the Julian calendar, named for the Roman Emperor Julius Caesar, who implemented it in 46 BC. The Julian calendar had calculated that it takes the earth 365-ΒΌ days to orbit the sun. However, it actually takes about eleven minutes less than that. Those eleven minutes accumulated each year until, by 1582, the calendar was 10 days out of harmony with the solar system.
On October ...