SEZ – Calendar
(Solar Earth Zodiac - Calendar)

SEZ – Calendar is solar, earth, zodiac calendar. Many calendars are in use at present. Most of them are since ancient times and have undergone many changes from time to time. Without going in detail history of calendars, we accept that the most widely used international calendar at present is Gregorian calendar which is a modification of Julian Calendar and was applied on 24th Feb. 1582AD("anno Domini" era)1 and is named on pope Gregory XIII. Years in the calendar are numbered from traditional birth year of Jesus. This calendar also needs rectification.

Now we are spreading out our wings towards space to quiet our curiosities about solar system and galaxy. Since we all belong to planet earth, so we should live like a family of Earth and adopt a common calendar based on revolution of our earth in zodiac around Sun. To avoid any discrepancies a new solar calendar is badly needed with the start of 3rd millennium AD This is done by preparing a SEZ-calendar which is scientific and nature based. The calendar is based on revolution of earth around sun passing across different signs of zodiac starting from vernal equinox, tropical (sayana) longitude. The said calendar has synchronization with seasons, solstices and equinoxes along with start and end of a month with duration taken by earth during revolution across respective sign sequentially.
Like the Gregorian solar calendar, up to 2000 years it is also an arithmetical calendar and counts days as the basic unit of time grouping them into weeks, months and years. The calendar repeats completely every 730,485 days of 24 hours each, 104,355 weeks of seven days each, 24,000 months and 2,000 years (having 1515 years of 365 days and 485 leap years of 366 days).Thus completing a cycle of 2,000 years. This gives an average year length of exactly 365.2425 days i.e. 365 days, 5 hours, 49 minutes and 12 seconds.

But since the mean tropical year is of 365.242190 days2 i.e. 365 days, 5 hours, 48 minutes and 45.216 seconds with a difference of 26.784 seconds (0.00031 day) per year i.e. 14 hours, 52 minutes and 48 seconds (0.62 day) per 2,000 years. So we can say difference of 31 days in 1 lakh (1/10 million) years.
This difference is nullified in SEZ-calendar by creating astronomical days, so that the calendar becomes almost perfect in itself. Hence updating is required after every 2,000 years.

Leap Days :-
Length of the mean tropical solar year (equinox to equinox) = 365.242190 days.
In SEZ-calendar complete solar days in a solar year i.e. 365 will have their own identity and part of a day (0.24219) will have its own identity. So the leap days will have their own identity and will be known as "leap days” (LD).Hence the no. of days in a leap month will also remain constant without any change.

To Calculate No. Of Leap days:

  • 1 every 4th year
  • 24 every 100 years, and
  • 97 every 400 years.
  • 485 every 2,000 years, but
  • 484 (if astronomical day 485-1) &
  • 24219 every 1,00,000 years
    (after deduction of astronomical days 24,250 – 31)

Alternately :-

No. of leap days in one lakh years :-

@ one leap day in years divided by 4 = 25,000
Less : 3 leap days in century years not divisible by 400 = -750
Less : 31 days in one lakh years as astronomical days = -31
Total = 24,219 days

To Calculate Total No. Of Solar Days :-

365 days / solar year + No. of leap days (LD) – No. of astronomical days.
So total no. of solar days in 100,000 solar years will be:-
(365 x 100,000) + (97x250) – 31*
= 36,500,000 + 24,250 – 31*
= 36,524,219 days / lakh year.
(N.B.:- 31* is the number of astronomical days in 1 lakh years.

Astronomical Day :-
In SEZ- calendar there is a provision of updating. In the years divisible by 2,000 the association of astronomers from all around the world will decide the difference of time between beginning of SEZ-calendar year and tropical vernal equinox (ecliptic longitude) year including slowing down of earth's rotation (tidal acceleration and leap second), slight variation in duration of vernal equinox year and changes occurring in time due to nature from time to time. If the time difference is less than 12 hours including all factors. This will be known as astronomical day and the year will not be a leap year (omitting of leap day) i.e. the astronomical day will be subtracted from routine no. of leap days by calculations. If the difference in more than 12 hours considering all factors, there will be a routine leap year. The no. of astronomical days is 31 in a period of 100,000 years with respect to the mean tropical year of 365.24219 days. If required astronomical days may increase or decrease in number accordingly to have synchronization of SEZ-calendar year and vernal equinox year with difference in hours only possibly less than 12 hours. Number of astronomical day will be one and sometimes two in a period of 4,000 years.

Beginning Of The Year :-
First month & first date of SEZ- calendar will start when the earth is on vernal equinox, a point of intersection of the ecliptic with celestial equator, so called first point of Aries (0o Aries) which is the ascending node of the Sun in relation to the ecliptic on the equator, when it passes from south to the north. The other months will be according to the sequence anticlockwise.

Months :-
SEZ-calendar is divided into twelve months of irregular length (having equal angular distance of 30o each in revolving earth path). Duration of month is in accordance to the duration taken by revolving earth across respective sign. According to Kepler’s 2nd law of revolutionary planets more time is required for crossing 30o angular distance when the sun is at aphelion (earth being farthest from sun) and less time required when the sun is at perihelion (earth being nearest to sun). Duration of SEZ-Calendar month and revolution time of earth across respective sign in zodiac will differ in hours only (<12 hrs).
Name of months may be either of the following choices.

  • Digital – starting from 1 to 12.
  • In accordance to capital letter of the English alphabets in sequence starting from A to L.
  • In accordance to name of tropical signs starting from Aries to Pisces.
  • According to the decision taken by international association of astronomers after seeking advice of people on earth.

 Table Showing Beginning of Solar Months and Their Duration :-

Gregorian Calendar date
Name of Solar months (Choices) Duration in days
21 March 1 A ARI 30 / + "LD"
20 April 2 B TAU 31
21 May 3 C GEM 31
21 June 4 D CAN 32
23 July 5 E LEO 31
23 August 6 F VIR 31
23 September 7 G LIB 30
23 October 8 H SCO 30
22 November 9 I SAG 30
22 December 10 J CAP 29
20 January 11 K AQU 30
19 February 12 L PIS 30

Week :
Week days and weeks will remain in the same pattern and sequence as they are at present without any change.

Occurrence Of Leap Day In A Solar Year :-
The leap day (intercalary day in a leap year) will take place at the end of 1st month (A, 1, Ari.) and before the start of 2nd month (B, 2 Tau.). When the earth has almost crossed sign Aries during its revolution and will be known as "LD" (Leap Day). Thus not affecting the dates of solstices and equinoxes as well as no. of days in a month. So the first solar month in a leap year will be of 30 days + "LD" (Leap Day) if any.
Since the revolution time of northern hemisphere is more than 186 days (186.4 days) & of southern hemisphere is less than 179 days (178.8 days) & revolution time across sign Aries is nearly 30.4 days, so the leap day will take place at the end of first month only. By doing so, the dates of solstices and equinoxes will remain same every year and not changed due to leap day.

Beginning Of SEZ-Calendar And Writing Of Date, Month & Year :-
The months are identified by capital letter of English alphabets sequentially starting from A or by number starting at 1 or by name of present signs or by the name applied for them unanimously. The day of the month numbered sequentially starting at 1.

To avoid any short of complications and to make it easy:
SEZ-calendar can be started from back date i.e. 21st March, 2001 AD of Gregorian Calendar. This date being 1st date of 1st month and 1st year of SEZ-calendar e.g. 21st March, 2001 AD at 24 hours mid night will be 1st , A, 0001 of SEZ-calendar; representing 1st – date of month, A-First month and 0001 start of First year of SEZ-calendar. The new year to be celebrated at this time every year.

N.B:- If astronomical day is required at the onset of calendar, zodiac calendar will start from 21st March, 2,000 and astronomical day will take place at the end of first month. This will be known as "0" (Zero) astronomical day and "0" (zero) year. With the view that the SEZ-Calendar was started on 21st March, 2,000 but practically applied since 21st March 2001 AD. This year will not be counted. This is only to update the time before starting SEZ-calendar.
Table Showing SEZ-Calendar Date , Earth Entering Sign And Seasons With Their Duration In Days In Relation To G-Calendar

Ecliptic Sign Aries Taurus Gemini Cancer Leo Virgo Libra Scorpio Sagittarius Capricorns Aquarius Pisces
Date and season 1
1 1 1
1 1 1
1 1 1
1 1
SEZ-Calendar Month A B C D E F G H I J K L
G-Calendar Date 3* 214 20 21 21 23 23 23 23 22 22 20 19
G-Calendar Month 3* March April May June July August September October November December January February
No. of days / month 30+(LD) if any 31 31 32 31 31 30 30 30 29 30 30
Indian Season Vasanta Grishma Varsa Sarat Hemanta Sisira Vasanta (Cont.)
No. of days +30=60
If any
62 63 61 60 59 30
International Season Spring Summer Autumn Winter
No. of days 92
94 90 89
  • SEZ-calendar = Solar, Earth, Zodiac calendar
  • VE = vernal equinox
  • AE = autumnal equinox
  • G-calendar= Gregorian calendar
  • SS = summer solstice
  • WS = winter solstice
  • (LD) = occurrence of a leap-day
  • * = Astronomical start of tropical zodiac

N.B:- Solstices and equinoxes are in relation to northern hemisphere of earth. For southern hemisphere they will change accordingly.

4th month "D" (cancer) is a month of aphelion (Earth being farthest from sun) having 32 days.
10th month "J" (Capricorn) is a month of perihelion (Earth being nearest to sun) having 29 days.

 Advantages Of SEZ- Calendar :-
Solar year will start from first point of Aries a landmark i.e. vernal equinox (intersection of the ecliptic with celestial equator – the natural phenomena every year).

Solstices and equinoxes will be always on date 1st of a month e.g.:-
Vernal equinox      – onset of 1st month. (Aries)
Summer solstice    – onset of 4th month. (Cancer)
Autumnal equinox – onset of 7th month. (Libra)
Winter solstice       – onset of 10th month. (Capricorn)

Seasons (International as well as Indian) will synchronize with start and end of months with respective signs.
Duration of solar months will synchronize with duration taken by revolving earth across respective signs (difference being only in hours, i.e. <12 hrs.).

By representing leap day at the end of 1st month as a "LD" (Leap Day), no change in no. of days of a month having a leap day because leap days will have their own identity.

There is provision of updating the calendar, after every 2,000 years. Thus the difference of time between occurrence of vernal equinox and change of SEZ-calendar year will be only in hours (less than 12 hrs.) for indefinite time even if the changes take place by nature in future.

N.B.:-The leap day at the end of 1st month is in accordance to Kepler's Law because time taken in northern hemisphere is more than 186 days and in southern hemisphere less than 179 days. Time taken across sign Aries is nearly 30.5 days. Hence leap day after every 4th year at the end of 1st month (Aries) is quite justified.

This calendar is based on rotation and revolution of earth around Sun in zodiac. Days and Weeks remain same without any change. Total No. of months in one year are 12 which represent 12 signs and are in accordance to sequence of present 12 signs, starting from Aries to Pisces. The number of days differs in different months. Respective month synchronize with the duration taken by revolving earth across different signs. The average duration of one year is 365.242190 days (A tropical solar year) from VE to VE instead of 365.2425 days in Gregorian calendar. New Year starts on the day of vernal equinox, when the earth enters sign Aries. A point of intersection of the ecliptic with celestial equator, so called first point of Aries which is the ascending node of the Sun in relation to the ecliptic on the equator, when it passes from south to the north. The other months will be according to the sequence anticlockwise. Leap day falls at the end of first month every fourth year excluding centuries which are indivisible by 4. At the end of every 2000 years, omitting of leap day (Astronomical day) will be decided by the association of international astronomers by considering all the factors. Vernal  equinox, summer solstice, autumnal equinox and winter solstice falls on day 1 of first, fourth, seventh and tenth month respectively in northern hemisphere. Seasons also fall on date 1st every third month and Indian seasons fall on date 1st every two months.

Foot Note :

References :
Retrieved from online dated. 29.07.2007
World Book encyclopedia (2001)
Calendar: Humanity's Epic Struggle To Determine A True and Accurate Year, David Ewing Duncan, Harper Perennial, 1999, ISBN 0-380-79324-

Dr. M. L. Agarwal

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