A civil calendar is a calendar in general use by public officials and private citizens. In most of the modern world, the civil calendar used is the Gregorian calendar system, created in 1582 by Pope Gregory the 13th. Many regions also have alternate calendars that mark cycles of religious events. Typically, a civil calendar includes only state or national holidays and is largely non-secular so as to allow for religious plurality.
Calendars are created primarily to regulate routine and behavior, and standardize the reckoning of time. The common civil calendar is based on the time it takes for the Earth to make a complete transit of the sun, which takes about 365.24 days. This cycle is divided into twelve months that consist of 28-31 days. Months are further divided into roughly four week segments, with each week containing seven days. In order to balance out the extra .24 days of each transit, the civil calendar adds an extra day to February once every four years.
Although the Gregorian calendar is the international standard throughout most of the modern world, this was not always the case. Before the age of easy transportation, most regions had their own calendars based on religious or civic systems. In the ancient Roman empire, most provinces operated under the Julian calendar, created by Julius Caesar. India and other Hindu regions used calendars created before the common era, though they went through several adaptations over the years. The Mayan calendar was devised around 6th century before the common era (BCE) and is noteworthy for its highly complex and advanced methods of development.
There are several important reasons for a civil calendar, each with particular significance. A common calendar allows the recording of major civic events and the ability to set certain actions on specific days of the year. In addition, the calendar works in accordance with the transit of the planet around the sun, allowing a general understanding of which seasons fall within which months. As scientific understanding has increased, calendars have typically become more accurate, which helps regulate seasonal preparation and agricultural activity.
A civil calendar will generally include important civic events, such as public holidays, which may vary from region to region. Additionally, specific days may be set that govern business or accounting behavior that relates to the government; in the United States, for instance, 15 April is the day when governmental tax forms are due each year. By maintaining a commonly used civil calendar throughout the world, governments and citizens are able to co-ordinate travel, business, and commerce with relative ease.