Which day does the Sabbath fall on?

     I am trying to discover which day the Sabbath falls on. I know it is defined as the seventh day, but are you sure that the seventh day is our Saturday? What if when they switched from the Julian calendar to the Gregorian calendar the days of the week get out of phase?

When the Julian calendar was switched to the Gregorian, ten days were omitted from the calendar, and it was decreed that the day following Thursday, October 4, 1582 (which is October 5, 1582, in the old calendar) would thenceforth be known as Friday, October 15, 1582. Although ten days were removed, the proper sequence of days in the week remained unchanged and continuous. Only numbers of the month were changed, not days of the week.
The Jews always kept the Sabbath every week without fail throughout history. Yahshua never corrected them on the day they kept as the Sabbath, and in fact He observed it Himself with other Jews on that same seventh day, Luke 4:16, 31,so we need only go back that far in history for the proper seventh-day sequence.