The Archetypes Calendar denotes days by means of three numbers, year-month-day, where the day number ranges from 1 through 30, the month number ranges from 1 through 13, and the year number is an integer (-2, -1, 0, 1, 2, 3, ...). Each year has 12 or 13 months, and each month has 29 or 30 days. Most years have 12 months. A year with 13 months is called a long year. More generally, an ARC year numbered y occupies position ((y + 1360) mod Y) + 1 in some ARC period, where Y = 1803. For example, ((4300 + 1360) mod 1803) + 1 = 252, so the year 4300 ARC has position 252 in some ARC period.