The human being, a social animal, has very high ideas about his own importance. This desire for posterity to remember him and his events made it necessary for them to record the incidents and relate them to the time when they occurred. In this ever-changing world, the Sun, Moon, and some planets can only be said to have some permanence. Our ancestors, as such, relied on the Sun and the Moon to measure TIME.
The rotation of the Earth around the Sun, the dawn of the morning, the arrival of night, were the first measurements of time. The arrival of the full Moon periodically was a second measure of time. The change of seasons and their recurrence was a third measure of time. Different nations had their own notions of measuring time, but the most prevalent today is the Gregorian Calendar, which has taken its one-year definition of the time it takes for the Earth to rotate once around the Sun and each minute consists of 60 seconds. .
The year was divided into months. The number of months had its origin in the number of gods in ancient Greek mythology. These months were subdivided into days, and the day itself was measured by the time it takes for the Earth to rotate once around its axis. The days were further subdivided, in this conception of time, into 24 hours, and each hour consisted of 60 minutes. For convenience, the days are grouped into what we call Weeks. Perhaps people wanted to take time off from their hard work and also wanted to set aside some time for their spiritual well-being. Thus, the week was divided into seven days, with Sunday generally being considered a day of rest and reserved among Christians for the prayers of Mass. Other religions also generally have a day reserved for prayers.
The time it takes for the earth to complete one revolution around the Sun, in our current Unit, is strange and not totally exact, which is why the leap year arose every 4 years. A normal year consists of 365 days, and a leap year has 366 days. However, this adjustment was not enough and a further adjustment required that there should be no leap years every 100 years, but again every 400 years has to be a leap year to keep time in tune with the Earth’s rotation.
Now dividing 365 days by 12 leaves a balance and because of this, there was inequality in the number of days in a month and again the number of weeks does not divide the month and the year completely and as such it is difficult to say exactly what the day of the week will fall in a particular month. Hence the need for a perpetual calendar that meets the needs of people for all times to come.
To build such a calendar, let’s look back at how we define our months and years. If we start from January 1 of a particular year, we find that the day of February 1 will differ from January by three. March 1, except in leap years, will be the same as February 1. On April 1 there will be three more than March and so on. From this, we get the first clue for our calculations.
52×7 = 364. Therefore, January 1 of the next year will be different from the previous year by one, except in the leap year when it will be different by 2. This gives us the second clue for our calculations.
On February 29, our calculations change, starting in March in the leap year and permanently for all other years. This, coupled with the fact that the year ’00’ will be a leap year only one out of four times, gives us our third and pretty much the last clue for our calculations.
Starting on January 1 of any year and knowing the day of that month, we can thus prepare the framework of our perpetual calendar without going into more details. Now I will give the final results. Let’s assign a number to each day of the week for convenience. I’ll start with Sunday as the number zero, Monday as one, and so on.
For January I give the number 1, for February the number 4 (in view of what was explained above in track (1)), the March number 4, the April number 0 (instead of 7 since the division by 7 leaves the remainder zero and we have 7 days in a week), the number 2 May, etc.
To calculate the day of the week for any date, we will have to add the base numbers for -) as indicated in the WORKING TABLE provided below, except that when the total is greater than 6 we will have to divide by 7 and take the reminder:
Basic number
0 for years: 01, 07, 18, 24, 29, 35, 46, 52, 57, 63, 74, 80, 85, 91; by months – April, July; for dates: 07, 14, 21, 28; for remainder ‘0’ after dividing the century by 4.
1 for the years: 02, 08, 13, 19, 30, 36, 41, 47, 58, 64, 69, 75, 86, 92, 97; by months – January, October; for dates – 01, 08, 15, 22, 29. –
2 for years: 03, 14, 20, 25, 31, 42, 48, 53, 59, 70, 76, 81, 87, 98; for months – May; for dates: 02, 09, 16, 23, 30; for remainder ‘3’ after dividing the century by 4.
3 for years: 04, 09, 15, 26, 32, 37, 43, 54, 60, 65, 71, 82, 88, 93, 99; for months – August; for dates – 03, 10, 17, 24, 31. –
4 for years: 10, 16, 21, 27, 38, 44, 49, 55, 66, 72, 77, 83, 94, 00; for months: February, March. November; for dates: 04, 11, 18, 25; for remainder ‘2’ after dividing the century by 4.
5 for years: 05, 11, 22, 28, 33, 39, 50, 56, 61, 67, 78, 84, 89, 95; by months – June; for dates – 05, 12, 19, 26. –
6 for years: 06, 12, 17, 23, 34, 40, 45, 51, 62, 68, 73, 79, 90, 96; by months – September, December; for dates: 06, 13, 20, 27; for remainder ‘1’ after dividing the century by 4.
In leap years, add “1” in the months of March through December.
The century counts from 1.101 to 31.12.2000, etc.
Note: For years ’00’ leap year only if the century is divided exactly by 4, that is, the remainder is 0.
METHOD: Add basic numbers for the day, month, year, remainder after dividing the century by 4 and the leap year. Divide the sum by 7, if the remainder is 1 – Monday; 2 – Tuesday; 3 – Wednesday; 4 – Thursday; 5 – Friday; 6 – Saturday; 7 – Sunday.
Examples; –
Full date
1.1.2007 Basic number 1 for the date, 1 for the month, 0 for the year, 6 for the century, 0 for the leap year, Total – 8 remaining after dividing by 7, 1 for what the day is – Monday .
9.3.2008 Basic number 2 for the date, 4 for the month, 1 for the year, 6 for the century, 1 for the leap year, Total – 14 remaining after dividing by 7, 0 for what the day is – Sunday .
12.31.2000 Basic number 3 for the date, 6 for the month, 4 for the year, 0 for the century, 1 for the leap year, Total – 14, remainder after dividing by 7, 0 for what the day is – Sunday.
1.1.2001 Basic number 1 for the date, 1 for the month, 0 for the year, 6 for the century, 0 for the leap year, Total – 8 remaining after dividing by 7, 1 for what the day is – Monday .
11.21.1763 Basic number 0 for the date, 4 for the month, 0 for the year, 4 for the century, 0 for the leap year, Total – 8 remaining after dividing by 7, 1 for what the day is – Monday .
1.3.1848 Basic number 1 for the date, 4 for the month, 2 for the year, 2 for the century, 1 for the leap year, Total – 10 remaining after dividing by 7, 3 for what the day is – Wednesday .
2.1.1976 Basic number 2 for the date, 1 for the month, 2 for the year, 0 for the century, 0 for the leap year, Total – 5 remaining after dividing by 7, 5 for what the day is – Friday .
25.6.2492 Basic number 4 for the date, 5 for the month, 1 for the year, 6 for the century, 1 for the leap year, Total – 17 remaining after dividing by 7, 3 for what the day is – Wednesday .
18.11.4567 Basic number 4 for the date, 4 for the month, 5 for the year, 4 for the century, 0 for the leap year, Total – 17 remaining after dividing by 7, 3 for what the day is – Wednesday .
26.1.2011 Basic number 5 for the date, 1 for the month, 5 for the year, 6 for the century, 0 for the leap year, Total – 17 remaining after dividing by 7, 3 so the day is Wednesday.
