Tradition

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

Solar gathers twelve calendars that fix the year to the sun rather than the moon, ranging from the third millennium BCE to a calendar designed in 2003.

The Ancient Egyptian Civil Calendar is the oldest: 365 days in three seasons of four thirty day months, closed by five days kept as the birthdays of Osiris, Horus, Set, Isis and Nephthys, with no leap day, so it drifted slowly through the true year while the ideal new year stayed tied to the heliacal rising of Sirius. The Coptic Calendar continues that same twelve month structure, now fixed by a leap day every fourth year, dated from the Era of the Martyrs in 284 CE, governing the feasts of the Coptic Orthodox Church. The Julian Calendar corrected that drift with a leap year rule and remains liturgically alive: the churches of Jerusalem, Russia, Serbia and Georgia still keep their fixed feasts by it. The Gregorian Calendar refined that rule further in 1582 and is now the world's civil standard.

Three mark a religious break from a neighboring system: the Ethiopian Calendar keeps its own Incarnation era seven to eight years behind the common era; the Zoroastrian Calendar assigns each day and month to a divinity under three concurrent reckonings; and the Nanakshahi Calendar, adopted in 2003, fixes Sikh festival dates to the Gregorian year rather than the lunar Bikrami calendar it replaced.

Two Mesoamerican counts, the Aztec Xiuhpohualli and the Maya Haab, share an eighteen month, 365 day structure closed by five unlucky days. The Badi calendar of the Baha'i Faith divides the year into nineteen months of nineteen days. The Old Icelandic Misseri calendar and Auguste Comte's nineteenth century Positivist calendar show the same solar problem worked out independently, one in medieval Iceland, the other in the Paris of 1849.