Shabad Kirtan: “Phalgun Anand Upaarjana – Barah Maha Manjh” by Bhai Harjinder Singh Ji.  Thank you Ji for the wonderful shabad.  (Source: Shabad Gurbani on YouTube)

By Harnaak Singh

We will now continue with the study of calendars.  We will start our discussion on Indian calendars and their concepts.

Note that we will continue with the figure number from Part 2.

I will be using planetary calculation programs Star Fisher (Tropical calculation method) and Jagannatha Hora (Indian Calculation method) for determination of planetary positions, equinoxes or any other calendar data related to the heavens.  These programs are available for free download at



Please download these software and use them to obtain the values I have presented in this study if you wish to.  You can check them and let me know is there are any errors.


In India generally the use solar or lunisolar calendars is practiced.  There are many Indian solar and lunisolar calendars in use depending on the region.  Figure 10 shows the regions in various colours and lists the basic type of calendar used.

Figure 10: Indian regions and calendars (picture source: C L Leow, “Indian Calendars” Thesis, NUS, 2000/2001)

10 IndianCalendars

As seen from Figure 10, the main types of calendars are

  • amanta (dark moon, massia) lunisolar calendar
  • purnimanta (full moon, puranmasi) lunisolar calendar
  • solar and religious amanta (dark moon, massia)  lunisolar calendar
  • solar and religious purnimanta (full moon, puranmasi) lunisolar calendar
  • National solar calendar, the Saka calendar (not listed in Figure 10). 

All the Indian calendars have many local variations but they all use the same calendrical principles found in an ancient astronomical treatise called Surya Siddhanta (see Figure 11).  

NOTE: In the Jagannatha Hora I have set the calculation setting to Surya Siddhanta method which is the sidereal method that uses the reference Citra (Spica in English) Star as the marker for 0 deg Libra.

Figure 11: Extracts from the Suria Sidhanta

11 Surya Siddhanta front

Surya Siddhanta

The Surya Siddhanta contains rules to construct the Indian solar and lunisolar calendars and includes formulae and equations to find the position of the Sun and other luminaries in the sky.  It is believed to have come into use around 400 AD.

The astronomical values and positions obtained by the Surya Siddhanta methods are not as accurate as modern methods.  For example the mean length of the sidereal year from the Surya Siddhanta is 365.2564 and from modern methods is 365.259756 which is a difference of 3 min 23.56 seconds (source: C L Leow, “Indian Calendars” Thesis, NUS, 2000/2001).

The Surya Siddhanta is however still used by the calendar makers, also called panchang makers though a trend towards modern methods has been observed.

Panchang (Jantri)

The calander makers (or pachang makers) write or prepare a panchang (calendar).  See example in Figure 12.  The panchang is an annual publication which lists calendrical information on celebration of festivals, performance of ceremonies or rites or astronomical and astrological data.

Figure 12: Example of a page from Panchang

12 Panchang

Some Indian Calendars

As stated above there are many Indian calendars.  The main ones are shown in Figure 13.  The corresponding Georgian calender dates for the different Indian calendars equivalent to 1st Kartika Saka 1918 are listed.

Figure 13: Some Indian calendars (source: C L Leow, “Indian Calendars” Thesis, NUS, 2000/2001)

13 Indian Calendar Common

Notes on calendars listed in Figure 13:

Refer to Figure 10 for the regions the calendars are used.

The solar calendars comprise the Orissa, Tamil, Malayali and Bengal calendars. The Orissa calendar is followed in Orissa, Punjab and Haryana. The Bengal calendar is used in West Bengal, Tripura and Assam. The Tamil and Malayali calendars are used in Tamil Nadu and Kerala respectively.  These use the sidereal year.  See Figure 10 for the map showing these regions.

The national calendar used the tropical year.

There are three types of amanta (new moon or dark moon) lunisolar calendars, namely, the Chaitra, Kartika and Ashadha calendars. The Kartika calendar is followed in Gujarat. In a place called Kutch found in Gujarat, people use the Ashadha calendar.

We will not address all the calendar types.  Since our interest is related to Sikhs and Gurbani, we will investigate the calendars related to Gurbani and Sikh historical calendrical records.  

Solar Eras and calendars

A era is a period marked by 

  • a distinctive character or 
  • reckoned from a fixed  point of event.

The eras related to the calendars is the solar era, the rotation of the earth round the sun being the marker for measurement of time in the era.  Some Indian eras are shown in Figure 14.

From the figure we see that Kali Yuga started in 3101/3102 BC and the Saka era used by the Indian National calender started in 79/80 BC.  

Figure 14: Eras used in Indian calendars (source: C L Leow, “Indian Calendars” Thesis, NUS, 2000/2001)

14 Eras

Other eras not mentioned but which are important for our study are the

  • Bikrami era which started in 57 BC and
  • Nanakshahi era which started in the Birth year of Guru Nanak Dev Ji, 1469 AD (This is the era that has also been used in the Sikh calender, called Nanakshahi e.g. 2018 AD is 549/550 Nanakshahi (Jan to mid-Mach 549 AND mid-March to December 550).
Indian Solar Calendar

We will now discuss some key concepts related to the Indian Solar calendars.  Though this section is for the Indian year/months we will where necessary compare it with the tropical year/months for comparison.

The Nirayana Year (Sideral Year)

The Indian solar calendars use the nirayana year which is the sidereal year.  We have studied the sidereal year in Part 2.  The important thing to note is that the sidereal year does not keep in line with the seasons.

Seasons based on sidereal and tropical coincide in 285 AD

The starting point of the nirayana year (sidereal year) coincided in 285 AD during March Equinox, SUN at ZERO degree ARIES which was on 20-MAR-285 10:48 PM (Star Fisher) and 20-MAR-285 10:36 PM (Jagannatha Hora).  Both methods show start of spring correctly at the Vernal Equinox which is the marker for start of spring.

In 285 AD both the nirayana (sidereal) year and the tropical year show spring correctly in March.  Figure 15 shows this scenario.

Figure 15: Calculated position of Earth using sidereal and tropical methods on 20-March-285 AD

15 EarthON-Mar-0285AD

Seasons showing drift of sidereal year against tropical year in 2018 AD

In 2018, on the March Equinox day (20-MAR-2018) based on nirayana year the SUN is in 5.95 deg PISCES.  There is a difference of 24.05 deg in nirayana (sidereal) year and spring is already into its 4th week.  Therefore the nirayana (sidereal) year does not follow the seasons.

On the other hand, the tropical year shows that the Vernal Equinox, which signals the start of spring, is on 20-March-2018 at 9:53 PM the SUN is at ZERO deg ARIES.  It correctly determines the start of spring.  Figure 16 shows this scenario.

The tropical year, however, follows the seasons.  

Figure 16: Calculated position of Earth using sidereal and tropical methods on 20-March-2018 AD

16 EarthON-Mar-2018AD

Seasons showing sidereal year drifts further against tropical year in 4000 AD

Now let us go further in time.  In the year 4000 AD the scenario is as follows:

Nirayana year:  On 20-MAR-4000 nirayana (sidereal) year is at 8.13 deg AQUARIUS, which gives a shift of 51.87 deg.  The nirayana year has moved further away from the vernal equinox,  with spring in its 8th week, showing that it keeps moving forward in the seasons as the years go by.  This is reflected in Figure 17.

Tropical year: Vernal Equinox ZERO deg ARIES is on 20-MAR-4000 at 6:49 AM again correctly aligned to the seasons.

Figure 17: Calculated position of Earth using sidereal and tropical methods on 20-March-2018 AD

17 EarthON-Mar-4000AD

The reason for the shift against the seasons in the nirayana (sidereal) year is “precession”, as we have studied in Part 2, of the equinox which we have explained in Part 2

Well you may be wondering how come the earth can be at TWO different positions at the same timeREMEMBER we are CALCULATING the position of the earth using TWO DIFFERENT METHODSThese methods are predicting the position of the earth differently because they use different way of calculating the position of the earth.

Let me show this with a simple example.  Let us consider Harmandar Sahib.  Refer to Figure 18  

Figure 18: Two views of Harmandar Sahib

18 Harmandir Sahib two views

Notice that View A is different from View B but Harmandar Sahib is the same.  The difference is because the two views are from different reference points.

This is the same with the earth being shown at two positions using different calculation methods.

If, at Harmandar Sahib, we are interested about going into the Darbar Sahib, then View A would be important as compared to view B.

Likewise if we are interested in the seasons on earth and plan for the seasons, then the tropical solar year would be more suitable because the seasons will come at the same time during the solar year.  We will know well in advance (10 years, 100 years and even 1000s of years) when they will occur.  We can plan ahead for whatever activities that are linked to the seasons.  On the other hand if we follow the sidereal year, there will be a need to calculate when the season will occur to make any sort time period based planning. 

So really as far as calendar is concerned, we will have to choose the calendar that suits the purpose.

The Solar month

The solar month is determined by the entrance of the sun into a zodiac sign until it goes into the next sign.

There are 12 zodiac signs and hence 12 solar months. Based on our assumption that the earth’s orbit around the sun is a circle, we would expect the months to have equal number of days.  This is not really the case since truly the earth’s orbit round the sun is an elliptic.  This is reflected in Figure 19.

Figure 19: Elliptical orbit and start of Nirayana year (source: C L Leow, “Indian Calendars” Thesis, NUS, 2000/2001)

19 Elliptic orbit

The sun is offset from the center.  The earth orbit is nearer to the sun at one end and further from the sun at the other.  Additionally the earth moves faster when closer to the sun than when it is further.  When it moves faster the month is shorter and the month is longer when the earth moves slower.

The elliptic is divided into sectors of 30 degrees each from the centre (sun) to signify the 12 months.  The start of the nirayana (sidereal) year starts with month (1).  The sectors signify the months (1) to (12).  The arc of each sector is equivalent to the number of days of the month.  The number of days in each of the months are not equal.  

Let us calculate the number of days in each month for March 2018 to March 2019.  We will do this using Jagannath Hora for nirayana (sidereal) case and as comparison use Star Fisher to find the equivalent for the tropical case.  The result is shown in Figure 20.  

Note that the results for are presented starting March 2018. The days per month are calculated from the date/time the sun enters the zodiac sign until it leaves the same zodiac sign or enters the next zodiac sign.  

For example consider March (refer to Figure 20).  For the Nirayana year the sun enters the zodiac sign Pisces on March 14 at 23:12 hours and enters zodiac sign Aries on 14-April at 7:42 hours.  The difference in days between these two is the number of days between 14-March and 14-April (which is equivalent to CHET).

On the other hand for the Tropical year the sun enters the zodiac sign Aries on March 20 at 21:39 hours and enters zodiac sign Taurus on 20-April at 8:39 hours. 

I have used the day to start from 12 midnight to 12 midnight (midnight day) as per the western calendar (this is how the software works).  However some Indian calendars use the day as that between sunrises (sunrise day).   It is important to understand this.  Consider 15-May in Figure 20.  The time of the sun entering Taurus is 4:32 am.  In the 12 midnight day, this would fall on 15-May but in the sunrise day this falls on 14-MaySee how the date can change.  

This is important when the start date of the month is picked for months CHET, VAISAKH etc.  We will come to this in later parts of this series of articles.

Figure 20: Days per month for Sidereal and Tropical year in 2018-2019

20 DaysPerMonth-2018

Notice the calculated days in the months are different.  This confirms the earth’s orbit is not a true circle, it is elliptic.

Some comments on the results in Figure 20.

  • The longest day is highlighted in light red background.
  • The shortest day is highlighted in light green background.
  • The longest and shortest days are 6 months apart.
  • For the Indian (sidereal) calculation, the sun moves into Aries on April-14 while in the Tropical the sun moves into Aries on March-20.  This clearly shows the impact of the precession of the equinoxes that we discussed above.  The Indian or sidereal method does not follow the seasonsThe shift of 25 days in 2018-9 is clearly apparent.  

Please do not hesitate to ask for clarification if you would like to understand further any of the concepts presented above.

We will stop here and continue with our discussion on Indian calendars in the next post.

Thank you for reading.  Hope you enjoyed the discussion.  

ਵਾਹਿਗੁਰੂ ਜੀ ਕਾ ਖਾਲਸਾ ਵਾਹਿਗੁਰੂ ਜੀ ਕੀ ਫਤਹਿ

To be continued

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