Calendar System And Different Types Of Calendars

Calendar System

Nowadays, there are several calendars that is used in India. The Indian government uses the Gregorian calendar for the administrative purposes. The Muslims uses the Muslim (Islamic) known as Hijri calendar. The Indian solar and lunisolar calendars, including their variations, are used for both civil and religious purposes and hence exert great influence on the daily activities of the people of India.

Classification of Calendars:

1. Solar Calendar

A solar calendar is a calendar whose dates specify the Season, they are almost equal to the apparent position of the sun relative to the stars.
The oldest solar calendars include the Julian calendar and the Coptic Calendar. They both have a year of 365 days, which is extended to 366 days at once in every four years, therefore they have a mean year of 365.25 days. 

The Gregorian calendar is a well-known example of a Solar calendar having a common year of 365 days and an also a leap year having 366 days.
every fourth year is a leap year unless it is a century year not divisible by 400.
However, the months of the Gregorian calendar never correspond to cycles of the Moon phase.

The Gregorian calendar was introduced in October 1582. This calendar is named after Pope Gregory XIII and is the most used calendar in the world. This calendar determines the Earth’s revolution around the Sun and spaces leap years to make the average year 365.2422 days long. It is the calendar used in the international standard for Representation of dates and times: ISO 8601:2004. It is a solar calendar based on a 365-day common year divided into 12 months of irregular lengths. The Gregorian calendar replaced the Julian Calendar, which had become 10 days out of synchrony with the solar cycle. In October 1582, 10 days were dropped from the calendar.   

 
Festivals according to Gregorian Calendar:
 January
1. New Year's Day- 1 January( First day of the Gregorian year)
2. Old New Year- 14th January (old ney year according to the old Julian Calendar)
3. 13 January-  Lohri
4. 14 january-   Makar Sankranti, Pongal, Lohri
February
5. 14 February- Valentines's Day
6. 12 February- Darwin's day
March
7. 21 March-  OstaraSpring Equinox
8. 8 March- International Women's day
9. Holi- (Holiday in honor of Lord Vishnu)
10. 28 March- Ram Navami (The birthday of Lord Rama is celebrated all over India.)
April
11. 8 April-  Hanamatsuri
12. 14 April (Secular)- Ramadan
13. Good Friday
14. Easter
15. 14 April- Traditional New Year
May
16. May 4- Star Wars Day
June
17. Ratha Yatra- Procession of Vishnu
18. Eid-ul-Fitr
July
19. Guru Purnima 
20. Eid-al-Adha
 August
21. Raksha Bandhan
22. Krishna Janmashtmi
23. Onam
24. International Friendship day
September
25. Labor day
October
26. Navratri- celebrate the conquest of goddess Durga
27. Diwali- (mid-October-mid November)
28. Kartika Purnima
29. 2 October- Gandhi Jayanti
30. 31 October- Halloween
 November
31. 19 November- International Men's day
 December
32. 8 December- Bodhi day
33. 25 December- Christmas Day
34. 31st December- New year's Eve


Solar calendars are basically of two types:

(i) Tropical Solar calendar
If the position of the world in its orbit around the Sun is estimated with reference to the Equinox, the purpose at which the orbit crosses the equinoctial circle, then it's dates accurately indicate the seasons.
That means they are synchronized with the declination of the Sun. These types of calendars are known as Tropical solar calendars.

Examples of Tropical solar calendars:-
1. Gregorian calendar
2. Bengali calendar  (It is national and official calendar of Bangladesh)
3. Iranian calendar
4. Indian National calendar (Saka Calendar)

(ii) Sidereal Solar calendar
If the position of the Earth is estimated with respect to the fixed stars, the dates indicate the zodiacal constellation near wich the sun can be found. This type of calendar in known as Sidereal solar calendar.

Examples of Sidereal solar calendar are:-
1. Hindu calendar
2. Tamil calendar
3. Bengali calendar
4. Malayalam calendar

2. Lunar Calendar

A lunar calendar consists of a number of lunar months with each month covering the period between two successive new moons or full moons. the lunar month  depends on the lunar cycle. A lunar year has 12 lunar months. Each month has an average length of about 29.5 days. This amounts to about 12 x 29.5 = 354 days a year, around 11 days shorter than the tropical year. 

Therefore, a lunar calendar ignores the tropical year and does not keep in line with the seasons. 

Example of Lunar calendar:- The Muslim calendar (Hijri/hijra) is an example of lunar calendar.

The Hijri calendar is also known as Lunar Hijri calendar which consists of 12 lunar months and 354/355 days. The Islamic year began in AD 622 during which the migration of Prophet Muhammad from Mecca to Medina, known as the Hijra happened. It has 354 days. It is used to date events in many Muslim countries simultaneously with the Gregorian calendar.
There are 12 months in the Hijri calendar which are given below:
1. Muharram
2. Safar
3. Rabia Awal
4. Rabia Thani
5. Jumaada  Awal
6. Jumaada Thani
7. Rajab
8. Sha’ban
9. Ramadan
10. Shawwal
11. Dhul-Qi’dah
12. Dhul-Hijjah     

Festivals according to Islam Calendar(Hijri/Hijra) :-
1. Al-Hijra — Islamic New Year. Marks the end of Mohammad's journey from Mecca to Medina.
2. Eid ul-Adha — Festival of Sacrifice
3. Eid ul-Fitr — End of Muslim Month of Fasting (Ramadan)
4. Prophet's Birthday -- Celebration of the birth of the Prophet Muhammad
5. Ramadan — Muslim Month of Fasting 

3. Luni-solar Calendar

A Luni-solar calendar is a combination of lunar calendars and solar calendars. This calendar is designed so that it can keep in phase with the tropical year using lunar months. The months of this calendar are based on the regular cycle of the Moon's phase. So lunisolar calendars are lunar calendars with – in contrast to them – additional intercalation rules being used to bring them into a rough agreement with the solar year and thus with the seasons.

The Chinese calendar is an example of a lunisolar calendar which consists of 12 lunar months, each month begins at the new moon.

History of Chinese calendar:

The Chinese luni-solar calendar is also known as Agriculture calendar. It is based on the concept of Yin Yang and astronomical phenomena which says about the movements of the Sun, Moon, Mercury, Venus, Jupiter and Saturn which are callled as Seven luminaries.

The Chinese calendar wese first recorded in the Zhou Dynasty (1050 BC - 771 BC). The Chinese luni-solar calendar has been evolved with many variations and changes throughout history. It also evolved with different dynasties including the "Six ancient calendars" in the Warring States period, the Qin calendar in the Qin dynasty, the Han calendar in the Han dynasty and Tang dynasty, the Shoushi calendar in the Yuan dynasty, and the Daming calendar in the Ming dynasty, etc. 
From the starting of 1912, the solar calendar is used together with the lunar calendar in China.

Festivals according to the Chinese luni-solar calendar:

Spring Festival, Chinese New Year, Lantern Festival, Mid-Autumn Festival, Dragon Boat Festival, Qingming Festival, etc.
The popular Chinese Zodiac is classified based on the Chinese calendars that assign an animal and its reputed attributes to each year in a repeating 12-year cycle.

Astronomical and Arithmetical Calendars

The calendars can be classified as calendars that are operated by straightforward numerical rules known as arithmetical calendars. 
The Gregorian calendar is an example of an arithmetical calendar. In an Arithmetical calendar,  A normal year has 365 days and a leap year has 366 days. Every fourth year is a leap year unless it is a century year not divisible by 400. Also, the lengths of months in this calendar are fixed with February having 28 days in a normal year and 29 days in a leap year. There is an arithmetical formula to determine which year is a leap. Together with lengths of months being fixed, we can easily and accurately construct the Gregorian calendar for a year that is way ahead of our present year.

The Calendars that are mainly controlled by astronomical events are astronomical calendars. These calendars do have some arithmetical components. However, they are really close approximations to their related astronomical events. The Indian solar calendars are astronomical calendars. Lengths of the calendar year and solar months are determined by the time taken for the Sun to travel along certain paths along the ecliptic. The process of rounding the lengths to whole numbers depends on a set of rules involving the occurrences of some astronomical events. Since the times of astronomical events vary from year to year, lengths of the calendar year and solar months also vary. Hence we cannot formulate any arithmetical rules to determine their lengths.