Understanding the Calendar
By the 16th century the slight miscalculations of the old Julian calendar had reached a point where the calendar months no longer corresponded with the solar year.
For that reason Pope Gregory XII proclaimed a new, improved calendar in Feb 1582; at that time the introduction involved jumping forward 10 days.
The Gregorian calendar ran into resistance, especially in the Reformed areas. In Switzerland it was introduced slowly, over the course of 200 years. By the beginning of the 18th century it was widely adopted, but not everywhere.
Here are dates on which the remaining areas finally started using the Gregorian calendar:
1.1.1701 (new style: 12.1.1701): Reformed cantons of Zurich, Bern, Basel, Schaffhausen and the Catholic parts of Glarus, Neuchatel, Geneva
1724: City of St Gallen
4.7.1798: Reformed Glarus
Christmas 1798: Appenzell Outer Rhodes
The situation in Graubünden was particularly complicated.
In the mixed (Catholic/Reformed) communes the Catholics used the new calendar from the middle of the 17th century, but the Reformed members of the communes adopted it only from the middle of 18th century.
Reformed communes adopted the new calendar at various times between 1783 and 1812
The last to conform were Schiers and Grüsch, in 1812.
Between 1793 and 1805 the French revolutionary calendar was in force in those areas of Geneva and the Bishopric of Basel which France had annexed.
Britain and it's colony, the future Uniited States, adopted the Gregorian calendar on 14th September 1752.
This feature requires Flash player to be installed