Method to determine whether a year is a leap year - Microsoft 365 AppsSummary This article describes how to determine whether the year in a date that is used in a Microsoft Excel document is a leap year. More Information The date system that is used by Excel is based on the Gregorian calendar, first established in 1582 by Pope Gregory XIII. This calendar was designed to correct the errors introduced by the less accurate Julian calendar. In the Gregorian calendar, a
