Shabad Kirtan: “Jin Jin Naam Dhiyaya” by Bhai Hartirath Singh Sodhi. Thank you Ji for the soulful kirtan. (Source: Babli Singh on YouTube)
by Harnaak Singh
In these series of articles we explore the calendar issue in the Sikh Panth and the need of a calendar. Hopefully at the end of these articles we will all appreciate the problem is not to do with Hindu or Sikh or Christian or Bikrami etc. but to do with the heavens (constellation, sun, earth and moon). All the foolishness and stupidity the Nindaks are propagating will vanish.
A calendar is a system of marking or organizing social, religious, commercial or administrative events. The events can be past i.e. historical or future events. For the purposes of this article past events are considered as marked events while future events are considered as organized events. Essentially this is timekeeping. Timekeeping dates back to prehistoric period.
The natural timekeeping units were the day, solar year and lunation. Calendars were the method used for timekeeping. A day is the period between successive sunrises and has 24 hours. The solar year or tropical year is the period for one complete revolution of the earth round the sun. It is approximately 365.24219 days. Lunation or lunar month is the period between successive new moons. It is 29.531 days per orbit round the earth.
We will not go into history but will refer to some important calendar systems which will help us in this article. We will also look at planetary mechanics which is important to understand to make our discussion easier as we progress on the topic of calendar.
The Julian calendar
The Julian calendar was proposed by Julius Ceaser in 46 BC. It took effect on 1st January 45 BC. It had a regular year of 365 days divided into 12 months and a leap year was added every 4 years. The average Julian year was 365.25 days and was supposed to approximate one solar year. However the solar year (tropical year) which was 365.24219 is shorter but it was not compensated for in the Julian calendar. As a result the Julian Calendar gains 3 days every 4 centuries which gives approximately 1 day in 128 years.
The problem that arises is that there is misalignment with seasons over time. This misalignment is observed in that the date of commencement of spring starts to come earlier and earlier over time. Spring begins with the summer equinox (northern hemisphere) which is generally 21st March.
Before we move on to more calendars let us discuss the moon, earth, sun and the constellation which is very much related to calendars and timekeeping. We will then understand what equinox means.
Moon, Earth, Sun and the Constellation
Figure 1 shows the earth, sun and the constellation, it is worth discussing Figure 1 as it is very important. The sun (yellow colour) is shown in the centre. The earth orbit around the sun is shown in blue. The outer cylinder is the heavens in our galaxy of which the 12 major constellations, Aries, Taurus … Pisces are shown. The months Chet, Vesakh …. Phagan are also shown together with the English months, March-April, April-May …. February-March, related to the constellations. The numbers (based on northern hemisphere) in the earth’s orbit around the sun are
- 1: Summer equinox
- 2: Summer solstice
- 3: Winter equinox
- 4: Winter solstice
The equinox is a very important marker for the solar year and is also in understanding calendar systems. It marks the beginning of spring. It occurs on 21st March for the northern hemisphere. Equinox is when the day and night are of equal duration, the sun is shining directly overhead the equator. Solstice is when either the day is the longest, summer equinox, or the day is the shortest, winter equinox. In summer solstice, the sun shines directly overhead the tropic of cancer and in winter solstice, the sun shines directly overhead the tropic of Capricorn.
Figure 1: Earth Sun and the Constellation (papastronsay.blogspot.com.au)
Notice the white line through the earth in Figure 1. This line represents the axis through the earth’s North and South poles. This is reflected in Figure 2. The earth rotates around this axis and the rotation results in day and night. It is inclined at 23.5 degrees from its plane of orbit around the sun. The earth also orbits the sun, this movement round the sun causes the seasons.
Figure 2: Earth’s axis of rotation (source Irene Pennington Astronomy blog)
Just like the earth orbits the sun, the moon orbits the earth. The moon’s rotation is “in synchronous” rotation with the earth. This means the same side faces the earth always as it progresses through its rotation. It rotates around its axis once at about the same time it takes to rotate around the earth. Our interest lies in the phases of the moon. This is reflected in Figure 3.
Figure 3: Moon phases (source Wikipedia)
The moon orbits the earth. Figure 3 shows the phases of the moon as seen from the earth. The numbered phases are as follows:
- 1: New moon (massia)
- 2: First quarter
- 3: Full moon (puranmasi)
- 4: Last quarter
Note that new moon (massia) is when the moon is between earth and the sun (Figure 3 position 1) and full moon (puranmasi) is when the earth is between the moon and sun (Figure 3 position 3). First and third quarter is when the moon lies on its orbit around the earth. The new moon (massia) and full moon (puranmasi) are very important markers for the lunar month and also for understanding calendar systems.
The Gregorian calendar
The Gregorian calendar was introduced in 1582 by Pope Gregory. The purpose was to stop the drift of the calendar in relation to the seasons, essentially the equinoxes and solstices in the Julian calendar. Recall that the Julian calendar gains 1 day in 128 years.
The leap years were arranged so as to reduce the shift of the seasons. The rule for correction is
Every year divisible by 4 is a leap year, except for years exactly divisible by 100. These centurial years are leap years if they are divisible by 400.
This resulted in the mean year to 365.2425 (closer to the solar year which is approximately 365.24219). This gives an approximate error (gain) of 1 day in 3030 years, but considering that the constellation and earth are moving, this may be closer to 1 day in 7700 years. Figure 4 shows how this correction of shift is reflected at the summer solstice date of 21st June.
Figure 4: Gregorian calendar leap year adjustment (source Wikipaedia)
Notice, in Figure 4, how the date/time is adjusted when leap year correction is applied and what happens if no leap year correction is applied. The leap year adjustments are applied to keep the seasons occurring at about the same time yearly. Just imagine driving the car; we keep adjusting the steering wheel to keep the car in a straight line.
Also note, in Figure 4, the dashed line subsequent to 1800. This is what happens if the leap year correction rules (of no leap year every 100 years …) is not applied. It is like not making a correction on your steering and ending up in a ditch.
This is actually what happens with the Julian calendar and that is why by 1582 AD the seasons were out by 11 days. An 11 day correction was applied when the Julian Calendar was changed to Gregorian in 1582. See Figure 5. Notice 4th October on the Julian calendar was followed by 15th October on the Gregorian calendar (not 5th October).
Figure 5: 11 day correction applied when changing from Julian to Gregorian calendar (source Wikipaedia)
Even with the Gregorian calendar notice that in 1750 the solstice occurred at 21-June at about 2:30 am (see Figure 4) but in 2250 on 21-June the solstice occurs just on midnight (Figure 4). This shows approx. 2.5 hours shift in 400 years. This will give the shift of approx. 1 day in between 3030 to 7700 years we spoke about earlier. There will be a rule to apply a leap year in one of the year when it is supposed to be skipped closer to the time. In this way the seasons calendar timing will be maintained within a day.
Please understand this correction as well as the discussion on the constellation/sun/earth/moon because it is very important as we shall be talking about this in forthcoming articles. Ask questions if you are not clear.
The months and days per month are the same as the Julian calendar.
|Months||Days in month|
|February||28 (leap years: 29)|
We will stop here and continue next with discussion on other 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.