YEREVAN, JANUARY 13, ARMENPRESS: The Old New Year falls on January 14, being 13 days adrift from New Year in the Gregorian calendar. The new calendar was introduced in 1582. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter gravissimas. The reformed calendar was adopted later that year by a handful of countries, with other countries adopting it over the following centuries, Armenpress reports.

The motivation for the Gregorian reform was that the Julian calendar assumes that the time between vernal equinoxes is 365.25 days, when in fact it is presently almost exactly 11 minutes shorter. The error between these values accumulated at the rate of about three days every four centuries, resulting in the equinox occurring on March 11 (an accumulated error of about 10 days) and moving steadily earlier in the Julian calendar at the time of the Gregorian reform. Since the Spring equinox was tied to the celebration of Easter, the Roman Catholic Church considered that this steady movement in the date of the equinox was undesirable.

The New Year by the Julian calendar is still informally observed, and the tradition of celebrating the coming of the New Year twice is widely enjoyed: January 1 (New New Year) and January 14 (Old New Year).

Because of the Protestant Reformation, however, many Western European countries did not initially follow the Gregorian reform, and maintained their old-style systems. Eventually other countries followed the reform for the sake of consistency, but by the time the last adherents of the Julian calendar in Eastern Europe (Russia and Greece) changed to the Gregorian system in the 20th century, they had to drop 13 days from their calendars, due to the additional accumulated difference between the two calendars since 1582.

The tradition of the Old New Year has been kept in Armenia, Russia, Serbia, Macedonia, Belarus, Bosnia and Herzegovina, Georgia, Kazakhstan, Montenegro, Ukraine(Malanka), Wales and Switzerland (as alter Silvester). In the first half of the 20th century, segments of the Scottish Gaelic community still observed the feast and today, groups such as Edinburgh's Am Bothan see this as a convenient date for Gaelic events.