Calendar 2009 Wallpapers

Calender 2009 - photo wallpapers: A calendar is a system of organising days for a socially, religious, commercially or administratively useful purpose. This organisation is done by giving names to periods of time - typically days, weeks, months and years. The name given to each day is known as a date. Periods in a calendar (such as years and months) are usually, though not necessarily, synchronised with the cycles of some astronomical phenomenon, such as the cycle of the sun, or the moon. Many civilisations and societies have devised a calendar, usually derived from other calendars on which they model their systems, suited to their particular needs.[br]A calendar is also a physical device (often paper). This is the most common usage of the word. Other similar types of calendars can include computerised systems, which can be set to remind the user of upcoming events and appointments. As a subset, 'calendar' is also used to denote a list of particular set of planned events (for example, court calendar).[br]Days used by solar calendars: Solar calendars assign a date to each solar day. A day may consist of the period between sunrise and sunset, with a following period of night, or it may be a period between successive events such as two sunsets. The length of the interval between two such successive events may be allowed to vary slightly during the year, or it may be averaged into a mean solar day. Other types of calendar may also use a solar day.[br]Calendar reform: There have been a number of proposals for reform of the calendar, such as the World Calendar, International Fixed Calendar and Holocene calendar. The United Nations considered adopting such a reformed calendar for a while in the 1950s, but these proposals have lost most of their popularity.[br]Lunar calendar: Not all calendars use the solar year as a unit. A lunar calendar is one in which days are numbered within each lunar phase cycle. Because the length of the lunar month is not an even fraction of the length of the tropical year, a purely lunar calendar quickly drifts against the seasons. It does, however, stay constant with respect to other phenomena, notably tides. A lunisolar calendar is a lunar calendar that compensates by adding an extra month as needed to realign the months with the seasons. An example is the Jewish calendar which uses a 19 year cycle. Lunar calendars are believed to be the oldest calendars invented by mankind. Cro-Magnon people are claimed to have invented one around 32,000 BC.[br]

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