Roman calendar ancient Greek calendars; and the Gregorian calendar, which refined the Julian system to bring it into still closer alignment with the solar year and is the basis of the current international standard. Roman dates were counted inclusively forward to the next of three principal days: the first of the month (the kalends), a day less than the middle of the month (the ides), and eight days—nine, counting inclusively—before this (the nones). The original calendar consisted of 10 months beginning in spring with March; winter was left as an unassigned span of days. These months ran for 38 nundinal cycles, each
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