Gregorian calendar It also specifies its epact relative to 1 January, in contrast with the Julian calendar, which specified it relative to 22 March. The old date was derived from the Greek system: the earlier "Supputatio Romana" specified it relative to 1 January. During the period between 1582, when the first countries adopted the Gregorian calendar, and 1923, when the last European country adopted it, it was often necessary to indicate the date of some event in both the Julian calendar and in the Gregorian calendar, for example, "10/21 February 1750/51", where the dual year accounts for some countries already beginning their
Adoption of the Gregorian calendar calendar) and Myanmar (Burmese calendar), and other countries use a modified version of the Gregorian calendar, including Thailand (Thai solar calendar), Japan (Japanese calendar), North Korea (North Korean calendar) and Taiwan (Minguo calendar). While many religious organizations reckon their liturgical year by the Gregorian civil calendar, others have retained their own calendars. Alternative calendars are used in many regions of the world today to mark cycles of religious and astrological events. Use of different calendars had potential to cause confusion between contemporaries. For example, it is related that one of the contributory factors for Napoleon's victory at the Battle of