Calanders

Calenders are used by people to tell the day. Youc an see what day a Monday or Tuesday days will be, and how far away they are for example. A calender is a system of organizing days for a social, religious, commercial or administrative purpose. This organization 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 calender (such as years and months) are usually, though not necessarily, synchronized with the cycles of some astronomical phenomenon, such as the cycle of the sun, or the moon. Many civilizations and societies have devised a calender, usually derived from other calenders on which they model their systems, suited to their particular needs.

A calender is also a physical device (often paper). This is the most common usage of the word. Other similar types of calenders can include computerized systems, which can be set to remind the user of upcoming events and appointments.

As a subset, calender is also used to denote a list of particular set of planned events (for example, court calender).

The English word calender is derived from the Latin word kalendae, which was the Latin name of the first day of every month.

A full calender system has a different calender date for every day. Thus the week cycle is by itself not a full calender system; neither is a system to name the days within a year without a system for identifying the years.

The simplest calender system just counts time periods from a reference date. This applies for the Julian day. Virtually the only possible variation is using a different reference date, in particular one less distant in the past to make the numbers smaller. Computations in these systems are just a matter of addition and subtraction.