Shabad Kirtan: Mauli Dharti Maulya Akash by Bhai Harcharan Singh Ji.  Beautiful kirtan in Raaag.  (Source: ShabadKirtan on YouTube)

by Harnaak Singh

There has been substantial discussion on Guru Gobind Singh Ji’s birthday date.  

In this article we discuss the historical birthdate of POH Sudhi 7, 1723 Bikrami and its relationship with the Julian and Gregorian dates.  

The dates we generally use today are based on the Gregorian calendar.

Then we will consider Purewal’s proposed birthdate of 5-JAN as the birthday of Guru Gobind Singh Ji.  We investigate this in relation to the actual birthdate of POH Sudhi 7, 1723 Bikrami.

COMMON SENSE demands that at least the proposed date must point to the actual birthdate.  Otherwise the proposed date has merely been a waste of time.

UNFORTUNATELY this is the case of the Purewal’s proposed date of 5-JAN-1667 which points to POH Sudhi 11, 1723. 


Guru Gobind Singh Ji’s birthdate is POH Sudhi 7 Bikrami year 1723 (i.e. 1666 CE). 

This means that GGS Ji’s birthday was the seventh day after dark moon in the period (month) POH.  The period (month) POH falls between DEC and JAN.  

I shall calculate how this fits into the Julian and Gregorian calendars.

Using first method

From website dark moon (massia) in this period is given for Lahore, Amritsar and Patna as follows.  Figures 1, 2 and 3 show the massia for three different locations.  The massia for POH is boxed in red.

Figure 1: Moon Phases for Lahore in 1666 

171227 PIC 1 GGS Birthday - Purewal wrong

Figure 2: Moon Phases for Amritsar in 1666 

171227 PIC 2 GGS Birthday - Purewal wrong

Figure 3: Moon Phases for Patna in 1666 

171227 PIC 3 GGS Birthday - Purewal wrong

For Lahore dark moon occurs at 10:34 pm on 15-DEC-1666 (Julian calendar). 

For Amritsar and Patna dark moon occurs at 12:00 midnight on 16-DEC-1666 (Julian calendar). 

Note that for Amritsar and Patna dark moon occurs at midnight on 22nd night (considering 6pm 22-DEC to 6am 23-DEC as the night).  The online software states that there may be many minutes error in the time meaning that for Amritsar and Patna the time could be a few minutes before 12 midnight or a few minutes after.  I have disregarded this error in the analysis.  Another point to consider is that the times for Lahore are Pakistan time zone and for Amritsar/Patna Indian time zone.

From the online app, POH SUDI 7 gives:

Based on Lahore 22-DEC-1666 (Julian calendar). (15 + 7 = 22)

Based on Amritsar and Patna 23-DEC-1666 (Julian calendar).  (16 + 7 = 23)

Converting this to Gregorian calendar using website.  Figure 4 shows this.

Figure 4: Julian – Gregorian conversion

171227 PIC 4 GGS Birthday - Purewal wrong

Based on Lahore birthday of GGS Ji is 1-JAN-1667 (Gregorian calendar). 

Based on Amritsar and Patna birthday of GGS Ji is 2-JAN-1667 (Gregorian calendar).  

Note that this is the calculation by one method.  The error (of a few minutes) may impact the dark moon and hence the date.

Using second method (This uses Tropical Year)

The Dark moon for Patna is calculated using another software “The Instant Astrologer” which gives planetary positions using the western calculation method (uses Tropical year).  This software uses Gregorian dates. The idea was to use this software to determine “massia” in DEC 1666.  Massia is when the Sun and Moon are conjunct.

The dark moon falls on 26-DEC-1666 at 12:37 am (00:37 hrs).  See Figure 5 below.  Dark moon is when the Sun and Moon are conjunct meaning at the same degree location from earth centre in the heavens which in the figure is 4 deg 21 seconds in the Sign of Capricorn (see red box).  

Figure 5: Dark or New Moon for Patna in December 1666 – Angular Degree 

171227 PIC 5 GGS Birthday - Purewal wrong

The same is shown plot on a circle in Figure 6.  Notice the Sun and Moon are conjunct in this figure.

Figure 6: Dark or New Moon for Patna in December 1666 – Plot 

171227 PIC 6 GGS Birthday - Purewal wrong

Therefore POH Sudhi 7 Bikrami year 1723 (i.e. 1666 CE) falls on 2-JAN-1667 (26-DEC + 7 = 2-JAN).  Gregorian calendar

2-JAN-1667 Gregorian calendar works out to 23-DEC-1666 Julian calendar.

 Using third method (This uses Siderial Year)

Computation done using Indian Astrology Software “Jagannatha Hora” available at website.  This uses Siderial year.  “The Instant Astrologer” which was used in second method uses Tropical year.  There is a difference in the two of about 20 minutes the sidereal being longer.

Using Jagannatha Hora, the Massia occurs on 15-Dec-1666 (Julian) at 11:37 PM (see picture below).  

Figure 7: Dark or New Moon for Patna in December 1666 

171227 PIC 1 GGS Birthday - Purewal wrong

Therefore POH Sudi 7 falls on 22-DEC-1666 (15 [Massia]+7=22: Julian) and 1-JAN-1667 (Gregorian).  This explains the discrepancy between the results in the previous calculation and the accepted date of 22-DEC-1666 (Julian) for Guru Gobind Singh Ji’s birthday.

My opinion is that the calculation done to determine GGS birthday is using Siderial Year.  

Summary of the methods

Considering the three methods, the date of birth of GGS Ji is 1-JAN-1667 Gregorian which is equivalent to POS Sudhi 7, 1723 using the Sidereal Year or 2-JAN-1667 using the Tropical year.

The difference in dates is explained due to

  • the different methods of computation and
  • that the time falls close to midnight.

I am of the opinion that the date 22-DEC-1666 Julian year OR 1-JAN-1667 Gregorian year, commonly used now, is based on computation using the Sidereal year.


Birthday is a SINGLE EVENT. It is not repeated again

The Lunar phases or solar dates are merely reference points in time. They must point to the same event irrespective of which method is used.  This is simple common sense.

Though we might celebrate the event cyclically (Bikrami or Gregorian or any other) the absolute time of the event does not change.  This means that the event whether marked by Bikrami, Julian or Gregorian must point to the event correctly.

In the days of our Gurus the events were marked by the phase of the moon (days after MASSIA dark moon or new moon  – Sudhi; PURANMASI full moon, days after PURAN MASI – Vadhi) and the period or month (CHET, VAISAKH, … POH … PHAGAN).  

For periodic cyclic celebration of the event, a representative date is used for the event.  For example consider Guru Gobind Singh Ji’s birthday.  

In Bikrami that date is POH Sudhi 7.  So this celebration would be celebrated on POH Sudhi 7 every Bikrami year.

In Julian that date is 22-DEC every Julian year.

In Gregorian the date is 1-JAN every Gregorian year. 

Notice the date, POH Sudhi 7, 22-DEC or 1-JAN does not change yearly for each of the respective calendars. 

They are all correct in that they point to the single birthday event of Guru Gobind Singh i.e. POH Sudhi 7 Bikrami 1723 OR 22-DEC-1666 Julian OR 1-JAN-1667 Gregorian.

The key is that they must point to the one event of Guru Ji’s birthday of POH Sudi 7 1723 BIKRAMI or 22-DEC-1666 Julian or 1-JAN-1667.

From our Guru’s times we have been using the Bikrami dates.  However if Julian or Gregorian calendar was in use then, we would be using either the Julian or Gregorian dates for the periodic celebration. 

Note that the dates used must point to the actual event dates not be a pseudo date randomly pointing elsewhere like the Purewal’s Nanak Shahi calendar.

Now we consider Purewal’s Calender proposed date of 5-JAN every year.  Moving back to Guru Ji’s birthday, this would be 5-JAN-1667 as the Gregorian birthday of Guru Gobind Singh Ji.  

This proposed Purewal’s Nanak Shahi calendar points to the birthdate of Guru Gobind Singh being POH Sudi 11 which does NOT MATCH POH Sudhi 7, and is therefore NOT CORRECT.

How can a date be chosen, irrespective of calendar used, such that it does not point to the actual date of birth?  Simple common sense reveals this has no logical basis.



The only SENSIBLE POSITION to take is to REJECT Purewal’s proposed date of 5-JAN yearly for Guru Gobind Singh Ji’s birthday because it is pointing to the incorrect date of birth.


A simple common sense test shows that Purewal’s choice of 5-JAN as the birthdate of Guru Gobind Singh is wrong.

There is every reason to reject the Purewal’s calendar in favour of one that will at least point to the correct date of birth.

The above analysis is not from a calendar expert but from a layman perspective using simple common sense and available software or apps using basic scientific knowledge about planetary movements in the heavens. 

Anyone can understand this simple analysis.  Please make comments or contribute constructively on Gurvichar Facebook.

Thank you for reading.

Vaheguru Ji Ka Khalsa Vaheguru Ji Ki Fateh.