Gregorian calendar Gregorian equivalent of 29 February (Julian), to remember that 29 February is discounted. Thus if the calculated value is −4 the Gregorian equivalent of this date is 24 February. The year used in dates during the Roman Republic and the Roman Empire was the consular year, which began on the day when consuls first entered office—probably 1 May before 222 BC, 15 March from 222 BC and 1 January from 153 BC. The Julian calendar, which began in 45 BC, continued to use 1 January as the first day of the new year. Even though the year used for dates
Adoption of the Gregorian calendar the solar year on a 32-year cycle. Some countries in the Islamic world use the Gregorian calendar for civil purposes, while retaining the Islamic calendar for religious purposes. Saudi Arabia adopted the Gregorian calendar as its civil calendar at the end of 2016. Today, the vast majority of countries use the Gregorian calendar as their sole civil calendar. Countries which have not adopted the Gregorian calendar are Ethiopia (Ethiopian calendar), Iran and Afghanistan (Persian calendar). Some countries use other calendars alongside the Gregorian calendar, including India (Indian national calendar), Bangladesh (Bengali calendar), Nepal (Vikram Samvat), Pakistan (Islamic calendar), Israel (Hebrew