This is a rather simple, but the most efficient calendar reform proposal. Each year starts in the time zone where there is the midnight line in the moment of winter solstice. In this system the international date line is in this time zone for a year. Areas in the time zone can decide whether they want to be on the west side of the date line, with the next day being the first day of the new year, or on the east side, with the next day being the last day of the old year.