I get what you're saying, but if the government repealed the Gregorian calendar (and went back to Julian) that wouldn't change the day of the week. The day of the week is historically independent of the day of the month. Catholics and Protestants agreed on this in the calendar change. The original papal bull that set up the Gregorian calendar has Thursday 1582-10-04 followed by Friday 1582-10-15; Great Britain and colonies (if we're taking the US perspective) followed Wednesday 1752-09-02 with Thursday 1752-09-14.