Gregorian Calendar

Because the Julian year, averaging 365.25 days, was somewhat longer than the actual length of a solar year, which is known to be 365.242199 days, the discrepancy between the Julian calendar and the seasons had increased to 10 days by the late sixteenth century. 

  • Fixed holy days started to fall in the “wrong” season, both for the church and for farmers, who relied on specific holy days to schedule planting and harvesting. 
  • From the year 1582, Pope Gregory XIII issued a reform that removed 10 days; in that year, October 15 was the day following October 5. 
  • This adjustment, along with the removal of leap days in “century” years unless they were evenly divisible by 400 (e.g., 1600, 2000), rectified the calendar to the point that only rare “leap seconds” are required to keep months and seasons in sync today. 

The Gregorian calendar (N.S., or New Style), which was originally used exclusively in Roman Catholic nations, gradually gained acceptance across the West and is now used by the majority of the globe, at least for business and government.

You may also want to learn more about Global Calendar Systems here.