The modern Assyrian calendar was introduced in the 1950s, loosely based on the historical lunisolar Babylonian calendar. The year begins with the first sight of Spring. Its era was fixed at 4750 BC. This was inspired by an estimate of the date of the first temple at Ashur in the Middle Ubaid period, notably based on a series of articles published in the Assyrian magazine Gilgamesh, edited by the brothers Addi and Jean Alkhas and Nimrod Simono. As of April 1, 2007, it is the Assyrian year of 6757.