Prior to Common Unification, there was no consistent calendar across the many Mortalborn in the Head of the Greatwyrm. Most nations kept their own records on their own calendar systems, or simply did not believe in written record at all. During this conversion, many historical reports contained demonstratable false information or proved difficult to convert verbatim. Any events recorded pre-Unification were accordingly considered to be potentially inaccurate.
The calendar was composed of 13 months, each with 28 days, and every year was composed of 364 days. It was named to represent a "death" and "life" of the world: the first month was Rebirth, symbolizing the beginning of the year. The months that followed formed patterns: crops began to grow in Bloomdawn, Highbloom, and Bloomdusk; the days were longest and warmest in Gleamdawn, Highgleam, and Gleamdusk; days grew colder and crops were reaped in Gloomdawn, Highgloom, and Gloomdusk; and finally, the days were shortest and coldest in Bleakdawn, Highbleak, and Bleakdusk.
A group of three months was called a "season" (Long Bloom, Long Gleam, Long Gloom, Long Bleak), save for Rebirth, which was considered a special season unto itself that reset the year.