Gregorian, << gruh GAWR ee uhn, >> calendar is the calendar that is used in almost all the world today. All modern business uses its dates. Pope Gregory XIII established it in 1582 to correct the Julian calendar, which Julius Caesar put into effect in 46 B.C. The Julian calendar year was 11 minutes and 14 seconds longer than the solar year. By A.D. 1580, this difference had accumulated to 10 days. Pope Gregory dropped 10 days from October one time to make the calendar year correspond more closely to the solar year. Thereafter, an adjustment was made to leap years to correct regularly for the extra minutes. Normally, each fourth year continued to be a leap year in which February had an extra day. However, years marking the century would not be leap years unless divisible by 400. For example, 1600 and 2000 were leap years, but 1700, 1800, and 1900 were not. At present, the average Gregorian year is about 26 seconds longer than the solar year. See also Calendar .
