1. By Sheela vasantha kumari M.TECH (COS)
Calendar sytem By
Sheela vasantha kumari
M.TECH (COS)

2. Introduction
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.
Periods in a calendar (such as years and months) are usually, synchronized with the cycle of the sun or the moon.

3. CONT…. Calendars that contain one level of cycles:
week and weekday – this system (without year, the week number keeps on increasing) is not very common year and ordinal date within the year, e.g. the ISO 8601 ordinal date system
Calendars with two levels of cycles:
year, month, and day – most systems, including the Gregorian calendar (and its very similar predecessor, the Julian calendar), the Islamic calendar, and the Hebrew calendar year, week, and weekday – e.g. the ISO week date

4. Maya calendar
The Maya calendar is a system of calendars used in pre-Columbian Mesoamerica, and in many modern communities in highland Guatemala and in Veracruz, Oaxaca and Chiapas, Mexico.
The Maya calendar consists of several cycles or counts of different lengths. The 260-day count is known to scholars as the Tzolkin, or Tzolk'in.
The Tzolkin was combined with a 365-day vague solar year known as the Haab' to form a synchronized cycle lasting for 52 Haab', called the Calendar Round.

5. Maya calendar

6. Arithmetic and astronomical calendar
An arithmetic calendar is one that is based on a strict set of rules; an example is the current Jewish calendar. Such a calendar is also referred to as a rule-based calendar.
The advantage of such a calendar is the ease of calculating when a particular date occurs. The disadvantage is imperfect accuracy. Furthermore, even if the calendar is very accurate, its accuracy diminishes slowly over time, owing to changes in Earth's rotation.

7. Gregorian calendar
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.
Due to the Gregorian calendar's obvious connotations of Western Christianity, non-Christians and even some Christians sometimes replace the traditional era notations "AD" and "BC" ("Anno Domini" and "Before Christ") with "CE" and "BCE" ("Common Era" and "Before Common Era")..

8. Islamic calendar
The Islamic calendar, Muslim calendar or Hijri calendar is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in most of the Muslim countries (concurrently with the Gregorian calendar), and used by Muslims everywhere to determine the proper day on which to celebrate Islamic holy days and festivals.
The first year was the year during which the emigration of the Prophet Muhammad from Mecca to Medina, known as the Hijra, occurred.With an annual drift of 11 or 12 days, the seasonal relation is repeated approximately each 33 Islamic years.

9. Islamic Hijri Calendar 1434

10. Hindu calendar
The lunisolar Hindu calendars are some of the most ancient calendars of the world. The standardized Indian national calendar based on Saka era with 78 CE as the start of the calendar is a lunar Hindu calendar used by the government together with Gregorian calendar. However, it is not used by the general public which widely uses the Vikrami lunar calendar Vikram Samvat with 56 BCE as the start of the calendar for religious activities and festivals. Vikram Samvat is also the official calendar in Nepal. A lunar month may have 29 or 30 days. All Hindu calendars have about 360 days and they insert an additional 13th month (by repeating a month twice in that year) every few years to synchronize with solar calendar.

11. Fiscal calendars
A fiscal calendar generally means the accounting year of a government or a business. It is used for budgeting, keeping accounts and taxation. It is a set of 12 months that may start at any date in a year.
The US government's fiscal year starts on 1 October and ends on 30 September. The government of India's fiscal year starts on 1 April and ends on 31 March.

12. 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 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 usage of the word.

13. Bulgar calendar
The Bulgar calendar was a calendar system used by the Bulgars, a seminomadic people, originally from Central Asia, who from the 2nd century onwards dwelled in the Eurasian steppes north of the Caucasus and around the banks of river Volga.
The main source of information used for its reconstruction is a short 15th century transcript in Russian language called Nominalia of the Bulgarian Khans, which contains 10 pairs of calendar terms.

14. Religious Calendar
Religious holidays are determined by a lunisolar calendar that is based on calculations of the actual postions of the Sun and Moon. Most holidays occur on specified lunar dates (tithis), a few occur on specified solar dates.
The calendrical methods presented here are those recommended by the Calendar Reform Committee (1957). They serve as the basis for the calendar published in The Indian Astronomical Ephemeris

15. Religious calendar

16. Zodiac calendar

17. NAMES OF THE WEEKS Sunday- sun day Monday-moon day
Tuesday-mars roman god of war
Wednesday-mercury roman god of peace
Thursday-Jupiter it is the king of roman god
Friday-venus roman goodness of love
Saturday-Saturn day roman god of planting and harvest

18. THANK YOU