Currently used calendars
Calendars in widespread use today include the Gregorian calendar, which is the de facto international standard, and is used almost everywhere in the world for civil purposes, including in the People's Republic of China and India (along with the Indian national calendar). Due to the Gregorian calendar's obvious connotations of Western Christianity, non-Christians and even some Christians REMINDER PROGRAM sometimes justify its use by replacing the traditional era notations "AD" and "BC" ("Anno Domini" and "Before Christ") with "CE" and "BCE" ("Common Era" and "Before Common Era"). The Hindu calendars are some of the most ancient calendars of the world. Eastern Christians of eastern Europe and western Asia used for a long time the Julian Calendar, that REMINDER PROGRAM of the old Orthodox church, in countries like Russia. For over 1500 years, Westerners used the Julian Calendar also.
While the Gregorian calendar is widely used in Israel's business and day-to-day affairs, the Hebrew calendar, used by Jews worldwide for religious and cultural affairs, also influences civil matters in Israel (such as national holidays) and can be used there REMINDER PROGRAM for business dealings (such as for the dating of checks).
The Persian calendar is used in Iran and Afghanistan. The Islamic calendar is used by most non-Persian Muslims worldwide. The Chinese, Hebrew, Hindu, and Julian calendars are widely used for religious and/or social purposes. The Ethiopian calendar or Ethiopic calendar is the principal calendar used in Ethiopia and Eritrea. REMINDER PROGRAM In Thailand, the months and days have adopted the western standard, although the years are still based on the traditional Buddhist Calendar.
Even where there is a commonly used calendar such as the Gregorian calendar, alternate calendars may also be used, such as a fiscal calendar or the astronomical year numbering system[1].
[edit] Fiscal calendars
Main article: REMINDER PROGRAM Fiscal calendar
A fiscal calendar (such as a 5/4/4 calendar) fixes each month at a specific number of weeks to facilitate comparisons from month to month and year to year. January always has exactly 5 weeks (Sunday through Saturday), February has 4 weeks, March has 4 weeks, etc. Note that this calendar will normally need to add a 53rd REMINDER PROGRAM week to every 5th or 6th year, which might be added to December or might not be, depending on how the organization uses those dates. There exists an international standard way to do this (the ISO week). The ISO week starts on a Monday, and ends on a Sunday. Week 1 is always the week that contains 4 REMINDER PROGRAM January in the Gregorian calendar.
[edit] School calendars
A school calendar incorporates school dates, anniversaries, school masses and carnivals (e.g. swimming and athletic carnivals). School calendars also include many reminders for school students, staff and parents.
[edit] Gregorian Calendar with Easter Sunday
Calculating the calendar of a previous year (for the Gregorian calendar taking account of the week) is a relatively easy REMINDER PROGRAM matter when Easter Sunday is not included on the calendar. However, calculating for Easter Sunday is difficult because the calculation requires the knowledge of the full moon cycle. Easter Sunday is on the first Sunday after the first full moon after the Vernal Equinox according to the computus. So, this makes an additional calculation necessary on top of REMINDER PROGRAM the normal calculation for January 1st and the calculation of whether or not the year is a leap year.
There are only 14 different calendars when Easter Sunday is not involved. Each calendar is determined by the day of the week January 1st falls on and whether or not the year is a leap year. However, when Easter Sunday REMINDER PROGRAM is included, there are 70 different calendars (two for each date of Easter).
At-A-Glance 2004-2005 calendar
At-A-Glance 2004-2005 calendar
[edit] Physical calendars
A calendar is also a physical device (often paper) (for example, a desktop calendar or a wall calendar). In a paper calendar one or two sheets can show a single day, a week, a month, or a year. If a REMINDER PROGRAM sheet is for a single day, it easily shows the date and the weekday. If a sheet is for multiple days it shows a conversion table to convert from weekday to date and back. With a special pointing device, or by crossing out past days, it may indicate the current date and weekday. This is the most common REMINDER PROGRAM usage of the word.
The sale of physical calendars has been restricted in some countries, and given as a monopoly to universities and national academies. Examples include the Prussian Academy of Sciences and the University of Helsinki, which had a monopoly on the sale of calendars in Finland until the 1990s.
[edit] Calendars in computing
* Electronic REMINDER PROGRAM calendar
* Category:Calendaring standards
[edit] Layout
There are different layouts for calendars.
A table for each week
[edit] See also
* Calendrical calculation
* Calendar reform
* Real-Time Clock (RTC), which underlies the Calendar software on modern computers.
* Time for divisions smaller than one day
[edit] List of calendars
Main article: List of calendars
