Which calendar is used for the New Year's Eve celebration called Hogmanay in Scotland?

Hogmanay in Scotland is a New Year's Eve celebration based on the Gregorian calendar.

The Gregorian calendar is the civil calendar used in modern Scotland and defines December 31 as the final day of the year. Hogmanay celebrations therefore lead into January 1 according to the same calendar used for ordinary civic and international scheduling.

The calendar was introduced by Pope Gregory XIII in 1582 to correct accumulated drift between the calendar year and the astronomical seasons. It adjusted the leap-year rule used by the Julian calendar: century years are not leap years unless divisible by 400. This makes the Gregorian calendar more accurate over long periods.

Scotland adopted the Gregorian calendar in 1752, when Britain changed its civil calendar system. The change also affected the legal start of the year and produced the famous calendar adjustment in which dates were skipped. Modern Hogmanay should not be confused with celebrations based on lunar or religious calendars.