Calendar. A calendar is a system of organizing days for social, religious, commercial or administrative purposes.
This is done by giving names to periods of time, typically days, weeks, months, and years. A date is the designation of a single, specific day within such a system. Periods in a calendar (such as years and months) are usually, though not necessarily, synchronized with the cycle of the sun or the moon. Many civilizations and societies have devised a calendar, usually derived from other calendars on which they model their systems, suited to their particular needs.
A calendar is also a physical device (often paper). A calendar can also mean a list of planned events, such as a court calendar. The English word calendar is derived from the Latin word kalendae, which was the Latin name of the first day of every month. Calendar systems A full calendar system has a different calendar date for every day. The simplest calendar system just counts time periods from a reference date. Moon Calendar. Www.sullivanil.us/images/calendar.JPG. Calendar made of matches on Typography Served. Calendar. Lunar Calendar. A lunar calendar is a calendar that is based on cycles of the lunar phases.
Because there are slightly more than twelve lunations (synodic months) in a solar year, the period of 12 lunar months (354.37 days) is sometimes referred to as a lunar year. A common purely lunar calendar is the Islamic calendar or Hijri Qamari calendar. A feature of the Islamic calendar is that a year is always 12 months, so the months are not linked with the seasons and drift each solar year by 11 to 12 days. It comes back to the position it had in relation to the solar year approximately every 33 Islamic years. It is used mainly for religious purposes, but in Saudi Arabia it is the official calendar. The oldest known lunar calendar was found in Scotland; it dates back to around 10000 BP. Lunisolar calendars All these calendars have a variable number of months in a year.
Some lunar calendars are calibrated by annual natural events which are affected by lunar cycles as well as the solar cycle. Lunar Phase. The phase and libration of the Moon for 2013 at hourly intervals, with music, titles and supplemental graphics.
Animation of the Moon as it cycles through its phases, as seen from the Northern Hemisphere. The apparent wobbling of the Moon is known as libration. The apparent change in size is due to the eccentricity of the lunar orbit. The principal lunar phases are new moon, first quarter moon, full moon and last quarter moon. These are the instants when, respectively, the Moon's apparent geocentric celestial longitude minus the Sun's apparent geocentric celestial longitude is 0°, 90°, 180° and 270°. Names of lunar phases Phases of the Moon, as seen looking southward from the Northern Hemisphere. In Western culture, the phases of the Moon have been given the following names, in sequential order: A crescent moon above Earth's horizon is featured in this image photographed by an Expedition 24 crew member. Crescent Moon taken by MPG/ESO 2.2-meter telescope at La Silla.