The Hindu Calendar is of two types:

1. the solar calendar or the saura maana, and
2. the lunisolar calendar or the chaandra maana.

We will describe both in detail in this article.

The Basic Structure

The structure of the Hindu Calendar is of course composed of days making months making years. The system of describing days is the same in both the solar and lunisolar calendars. The system of describing months and hence years is what distinguishes the solar and lunisolar calendars from each other. We shall first describe the day, then the months and year of the solar calendar, and then the months and year of the lunisolar calendar. Then we shall speak about year numbering and the 60 names of the years.

The Day

The Hindu calendrical day starts with local sunrise. It is allotted five "properties", called anga-s. They are:

1. the tithi active at sunrise
2. the weekday
3. the nakshatra in which the moon resides at sunrise
4. the yoga active at sunrise
5. the karana active at sunrise.

Together these are called the panchaanga-s where pancha means "five" in Sanskrit. An explanation of the terms follows.

Tithi

The angular distance (measured anticlockwise) between the sun and moon as measured from the earth can vary between 0° and 360°. This is divided into 30 parts. Each part ends at 12°, 24° etc. The circle ends at 360°. The time spent by the moon in each of this parts (i.e. the time taken for the angular distance to change by 12°) is called one tithi.

The month has two paksha-s or fortnights. The first 15 tithi-s constitute the bright fortnight or shukla paksha and the next 15tithi-s constitute the dark fortnight or krishna paksha. Tithi-s are indicated by their paksha and ordinal number within thepaksha. The 15th tithi of the bright fortnight (full moon) is called puurnimaa and the 15th tithi of the dark fortnight (new moon) is called amaavaasyaa.

The tithi in which the moon is at the time of sunrise of a day is taken to be the tithi for the day.

Weekday

The weekdays are as usual seven. They are (starting from Sunday):

1. Ravi vaasara
2. Soma vaasara
3. Mangala vaasara
4. Budha vaasara
5. Guru vaasara
6. Shukra vaasara
7. Shani vaasara

There are many other variations of these names, using other names of the celestial bodies of the Sun, Moon, Mars, Mercury, Jupiter, Venus and Saturn. The word vaasara means "weekday".

Nakshatra

The ecliptic (circle on the sky in which the sun, moon and planets seem to move) is divided into 27 nakshatra-s, which are variously called lunar houses or asterisms. The starting point for this division is the point on the ecliptic directly opposite to the star Spica called Chitraa in Sanskrit. (Other slightly-different definitions exist.) It is called Meshaadi or the "start of Aries". The ecliptic is divided into the nakshatra-s eastwards starting from this point.

The names of the nakshatra-s are given below. As always, there are many versions with minor differences. The names in parentheses give roughly the correspondence of the nakshatra-s to modern names of stars. Note that nakshatra-s are (in this context) not just single stars but are segments on the ecliptic characterised by one or more stars. Hence you will find many stars mentioned for one nakshatra.

The nakshatra in which the moon lies at the time of sunrise of a day is the nakshatra for the day.

Yoga

First, the angular distance along the ecliptic of any object on the sky, measured from Meshaadi (as defined above) is called the longitude of that object. Now when the longitude of the sun and the longitude of the moon are added, they produce a value ranging from 0° to 360°. (Values greater than or equal to 360° must be reduced to less than 360° by subtracting 360°.) Now this is divided into 27 parts. Each part will now equal 800' (where ' is the symbol of the arcminute which means 1/60 of a degree.) Now these parts are called the yoga-s. They are labeled:

1. Vishkambha
2. Priiti
3. Aayushmaan
4. Saubhaagya
5. Shobhana
6. Atiganda
7. Sukarman
8. Dhriti
9. Shuula
10. Ganda
11. Vriddhi
12. Dhruva
13. Vyaaghaata
14. Harshana
15. Vajra
16. Siddhi
17. Vyatiipaata
18. Variiyas
19. Parigha
20. Shiva
21. Siddha
22. Saadhya
23. Shubha
24. Shukla
25. Braahma
26. Aindra
27. Vaidhriti

Again, minor variations many exist. The yoga that is active during sunrise of a day is the yoga for the day.

Karana

A karana is half of a tithi. Since the tithi-s are 30 in number, one would expect there to be 60 karana-s. But there are only eleven. There are four "fixed" karana-s and seven "repeating" karana-s. The four "fixed" karana-s are:

1. Kimstughna
2. Shakuni
3. Naaga
4. Chatushpaad

The seven "repeating" karana-s are:

1. Bava
2. Baalava
3. Kaulava
4. Taitila
5. Gara
6. Vanija
7. Vishti

• Now the first half of the first tithi (of the bright fortnight) is always Kimstughna karana. Hence this karana is "fixed".
• Next, the seven repeating karana-s repeat eight times to cover the next 56 half-tithi-s. Thus these are the "repeating"karana-s.
• The three remaining half-tithi-s take the remaining "fixed" karana-s in order. Thus these are also "fixed".

The karana active during sunrise of a day is the karana for the day.

The Month and Year of the Solar Calendar

Now that the days are defined, we shall speak of how the solar calendar reckons its months and year.

As has been previously noted, the sun is observed to travel along the ecliptic. The ecliptic is now divided into twelve parts called raashi-s, starting from the point of Meshaadi defined above and moving eastwards. They are:

1. Mesha
2. Vrishabha
3. Mithuna
4. Kataka
5. Simha
6. Kanyaa
7. Tulaa
8. Vrishchika
9. Dhanus
10. Makara
11. Kumbha
12. Miina

These are the Sanskrit equivalents of the zodiac – Aries etc.

The day on which the sun transits into each raashi before sunset is taken to be the first day of the month. In case the sun transits into a raashi after a sunset but before the next sunrise, then the next day is the first day of the month. (Minor variations on this definition exist.)

The days are then labeled 1, 2, 3…. till the first day of the next month.

Thus we get twelve months with varying lengths of 29 to 32 days. This variation in length is because the path of the earth around the sun is an ellipse. The months are named by the raashi in which the sun travels in that month.

The new year day is the first day of the month of Mesha. Currently, it occurs around April 15th on the Gregorian calendar.

This is the structure of the Hindu Solar Calendar.

The Months of the Lunisolar Calendar

When a new moon occurs before sunrise on a day, that day is said to be the first day of the lunar month. The days are not labeled separately from 1 as in the solar calendar, but the tithi is their only label. When two successive days have the sametithi, the latter is called an adhika tithi where adhika means "extra". Sometimes, one tithi may never touch a sunrise, and hence no day will be labeled by that tithi. It is then said to be a tithi kshaya where kshaya means "loss".

The lunar month names are:

1. Chaitra
2. Vaishaakha
3. Jyaishtha
4. Aashaadha
5. Shraavana
6. Bhaadrapada
7. Aashvayuja
8. Kaartika
9. Maargashiirsha
10. Pausha
11. Maagha
12. Phaalguna

Naming Lunar Months

The naming of the lunar months is somewhat complex. It is based on the raashi into which the sun transits within a lunar month, i.e. before the new moon ending the month.

Extra Months

There are twelve raashi names, there are twelve lunar month names. When the sun transits into Mesha raashi in a lunar month, then the name of the lunar month is Chaitra. When the sun transits into Vrishabha, then the lunar month isVaishaakha. So on.

When the sun does not at all transit into any raashi but simply keeps moving within a raashi in a lunar month (i.e. before a new moon), then that lunar month will be named according to the first upcoming transit. It will also take the epithet of adhikaor "extra". For example, if a lunar month elapsed without a solar transit and the next transit is into Mesha, then this month without transit is labeled adhika Chaitra. The next month will be labeled according to its transit as usual and will get the epithet shuddha or "clean". [Note that an adhika month is the first of two whereas an adhika tithi is the second of two.]

An adhika maasa (month) occurs once every two or three years.

Lost Months

Now if the sun transits into two raashi-s within a lunar month, then the lunar month will be labeled by the first transit and will take the epithet kshaya or "loss". Actually, the month "lost" is the month which would have been labeled by the second transit. For example, if the sun transits into Mesha and Vrishabha in a lunar month, then it will be called Chaitra kshaya. There will be no month labeled Vaishaakha. Sometimes a kshaya is named by both months, so: Chaitra-Vaishaakha Kshayain which case the implication would be that the two months have merged (for religious purposes, see below).

A kshaya maasa occurs very rarely. Known gaps between occurrence of kshaya maasa-s are 19 and 141 years. The last was in 1983 CE. Jan-15 through Feb-12 were Pausha(-Maagha) kshaya. Feb-13 onwards was (adhika) Phaalguna and notMaagha. Maagha was "lost" that year.

Special Case: If there is no solar transit in a lunar month but there are two transits in the next lunar month,

• the first month will be labeled by the first transit of the second month (as usual) and take the epithet adhika and
• the next month will be labeled by its first transit (as usual) and take the epithet kshaya.

By one calculation, the last such occurrence was in 1963 CE. Oct-18 to Nov-16 midday were adhika Kaartika. From then on to Dec-15 were Kaartika(-Maargashiirsha) kshaya. Dec-16 onwards was Pausha, not Maargashiirsha.

Handling of religious observances in case of extra and lost months

Among normal months, adhika months, and kshaya months, the earlier are considered "better" for religious purposes. That means, if a festival should fall on the 10th tithi of the Aashvayuja month (this is called Vijayadashamii) and there are twoAashvayuja months, the first adhika month will not see the festival, and the festival will be observed only in the second nijamonth. However, if the second month is Aashvayuja kshaya then the festival will be observed in the first adhika month itself.

A festival which is to be observed on a month that was lost will be observed on the corresponding "previous" i.e. kshayamonth. For example, the festival of Mahaashivaraatri which is to be observed on the fourteenth tithi of the dark fortnight ofMaagha was, in 1983 CE, observed on the corresponding tithi of Pausha kshaya, since in that year, Maagha was lost, as we mentioned above.

The Year of the Lunisolar Calendar

The new year day is the first day of the month of Chaitra. In case of adhika Chaitra or Chaitra kshaya the rules outlined above will apply.

Correspondence of the Lunisolar Calendar to the Solar Calendar

A lunisolar calendar is always a calendar based on the moon's celestial motion, which in a way keeps itself close to a solar calendar based on the sun's (apparent) celestial motion. That is, the lunisolar calendar's new year is to kept always close (within certain limits) to a solar calendar's new year.

Since the Hindu lunar month names are based on solar transits, and the month of Chaitra will, as defined above, always be close to the solar month of Mesha, the Hindu lunisolar calendar will always keep in track with the Hindu solar calendar.

Year numbering and names

The epoch (starting point or first day of the first year) of the current era of Hindu calendar (both solar and lunisolar) is BCE3102 January 23 on the proleptic Gregorian calendar (i.e. the Gregorian calendar extended back in time before its promulgation from 1582 October 15). Both the solar and lunisolar calendars started on this date. After that, each year is labeled by the number of years elapsed since the epoch.

This is a unique feature of the Hindu calendar. All other systems use the current ordinal number of the year as the year label. But just as a person's true age is measured by the number of years that have elapsed starting from the date of the person's birth, the Hindu calendar measures the number of years elapsed. Today (as of writing this on 2005-05-18) the elapsed years in the Hindu calendar are 5106 and this is the 5107th Hindu calendar year. Note that the lunisolar calendar year will usually start earlier than the solar calendar year.

Apart from this numbering system, there is also a cycle of 60 calendar year names, which started at the first year (at elapsed years zero) and runs continuously:

1. Prabhava
2. Vibhava
3. Shukla
4. Pramoda
5. Prajotpatti
6. Aangirasa
7. Shriimukha
8. Bhaava
9. Yuvan
10. Dhaatu
11. Iishvara
12. Bahudhaanya
13. Pramaathin
14. Vikrama
15. Vrisha
16. Chitrabhaanu
17. Svabhaanu
18. Taarana
19. Paarthiva
20. Vyaya
21. Sarvajit
22. Sarvadhaarin
23. Virodhin
24. Vikrita
25. Khara
26. Nandana
27. Vijaya
28. Jaya
29. Manmatha
30. Durmukha
31. Hemalambi
32. Vilambi
33. Vikaarin
34. Shaarvari
35. Plava
36. Shubhakrit
37. Shobhana
38. Krodhin
39. Vishvaavasu
40. Paraabhava
41. Plavanga
42. Kiilaka
43. Saumya
44. Saadhaarana
45. Virodhikrit
46. Paritaapin
47. Pramaadin
48. Aananda
49. Raakshasa
50. Nala
51. Pingala
52. Kaalayukti
53. Siddhaarthin
54. Raudra
55. Durmati
56. Dundubhi
57. Rudhirodgaarin
58. Raktaaksha
59. Krodhana
60. Akshaya

Eras

Hindu mythology speaks of four eras or ages, of which we are currently in the last. The four are:

1. Krita Yuga
2. Tretaa Yuga
3. Dvaapara Yuga
4. Kali Yuga

They are often translated into English as the golden, silver, bronze and iron ages. (Yuga means era.) It is believed that the ages see a gradual decline of dharma, wisdom, knowledge, intellectual capability, life span and emotional and physical strength. The epoch provided above is the start of the Kali Yuga. The Kali Yuga is 432,000 years long. The Dvaapara, Tretaaand Krita Yuga-s are said to be twice, thrice and four time the length of the Kali Yuga respectively. Thus they together constitute 4,320,000 years. This is called a Caturyuga.

A thousand and a thousand (i.e. two thousand) caturyuga-s are said to be one day and night of the creator Brahmaa. He (the creator) lives for 100 years of 360 such days and at the end, he is said to dissolve, along with his entire Creation, into the Eternal Soul or Paramaatman or Brahma (different from Brahmaa).

(Article contributed by Sri Ramana Sharma(email: jamadagni-at-gmail.com)