Mesoamerican Long Count calendar 20, 2012 (Gregorian Calendar), followed by the start of the 14th b'ak'tun, 13.0.0.0.0, on December 21, 2012. There are only two references to the current creation's 13th b'ak'tun in the fragmentary Mayan corpus: Tortuguero Monument 6, part of a ruler's inscription and the recently discovered La Corona Hieroglyphic Stairway 2, Block V. Maya inscriptions occasionally reference future predicted events or commemorations that would occur on dates that lie beyond 2012 (that is, beyond the completion of the 13th "b'ak'tun" of the current era). Most of these are in the form of "distance dates" where some Long Count date is given,
Calendar year length of 365.25 days, and the Hebrew calendar has an average length of 365.2468 days. The Islamic calendar is a lunar calendar consisting of 12 months in a year of 354 or 355 days. The astronomer's mean tropical year, which is averaged over equinoxes and solstices, is currently 365.24219 days, slightly shorter than the average length of the year in most calendars, but the astronomer's value changes over time, so William Herschel's suggested correction to the Gregorian calendar may become unnecessary by the year 4000. The calendar year can be divided into four quarters, often abbreviated as Q1, Q2, Q3,