Have you ever wondered how it is possible that there are dozens of different calendars around the world, depending on religion and other factors where each calendar has different months and different dates yet the weekdays are always the same. For example today is the 11th day of January in the year 2019, according to the Gregorian calendar; the 5th day of Pausha in the year 1940 according to the Marathi calendar and the 27th day of Maargazhi in the year 1940 according to the Tamil calendar. In the example I have given here, the years for the two Indian calendars match, however there are others where the year too would differ. Yet in all the calendars mentioned here, plus many more, the day of the week is always a Friday (Shukrawar in Marathi, Velli Kazhamai in Tamil).
Isn't it strange that irrespective of various historical beginnings, all contemporary calendars still in use share the same weekday? Of course, it would be chaotic and hilarious if each calendar were to also differ with respect to weekdays. Imagine someone fasting on Sunday because it is a Tuesday or Thursday in their own calendar. Over thousands of years, various calendars have been used and discarded and somehow the Gregorian calendar which was originally introduced as a refinement of the Julian calendar in 1582, has become the de facto calendar globally today. People have got used to the fact that the number of days in each month are not constant and vary from 28-31. There have been various calendars throughout history, with varying months and weeks, but these are not so relevant for this 'different' post on my blog today. If you are interested, you can read the history on Wikipedia here. You can also view the list of calendars here.
It would have been more rational (or symmetrical if that is the right word) to have 13 months of 28 days each month rather than 12 months of varying number of days. The extra day could be a global holiday - day zero or International Year Day. In fact, this was proposed in the early 20th century and discarded as an idea. It would have been a perpetually fixed calendar since all dates would now be a constant day of the week, for e.g. Monday 1 Jan 2024 would have been a Monday forever. A calendar like this would be the same each year, with no confusion whatsoever. A leap year would have two International Year Days instead of one. The perpetual calendar is however not the same as a fixed calendar.
The origin of the week is however intriguing. It is believed that the 7-day weekly continuum was first practiced in Vedic India, even before the period of the Mahabharata around 3000 BC. There are other hypotheses revolving around Judaism and A continuous seven-day cycle that runs throughout history paying no attention whatsoever to the phases of the moon was first practiced in Vedic India, dating much earlier than the period of the Mahabharata around 3000 BC. Other hypotheses show that the weekly period origin was also practiced in Judaism around 600 BC and biblical seven-day cycle.
The point is not about which hypothesis is correct - it is about a high likelihood that somewhere 5000 years ago or even earlier, there was something common and united, at least with respect to calendars. A week has seven days (named after the seven planets then known) primarily because it aligns with the lunar cycle. Therefore, the brilliant minds who aligned the overall year to the earth's revolution around the sun, also thought of a way in which one could keep track of lunar cycles. Ideally, if it is a new moon on the 1st day, it would be half-moon on the 8th day and full moon on the 15th day. Two weeks made a fortnight which would end with either a full moon or a new moon. Called 'Paksha' in Sanskrit and other Indian languages, the waxing moon or the 'Shukla Paksha' would occupy one fortnight and the waning moon or 'Krishna Paksha' would occupy the other.
Sounds great and even thought subsequent adjustments were made by way of introducing the leap year with one extra day, no adjustments were ever made for the lunar cycle. Unfortunately the moon does not take an exact 28 days to revolve around the earth or rotate around itself, but it takes 27.3 days and the lunar phase cycle (from one new Moon to the next) is 29.5 days, neither 28 nor 30 nor 27.3. Whilst the moon spends an additional 2.2 days playing catch up since the Earth is whirling around the sun, the astronomers prefer to use neither the solar nor lunar time, but sidereal time. Its all quite confusing and perhaps the modern calendar may never again get revised, inspite of the obvious advantages of having 13 equal months of 28 days each. And there are other disadvantages - for example how would corporates divide a year of 13 months into 'quarters'? What if a local public holiday was on a Sunday - it would then be a Sunday each year.
I am sure there are some ingenious minds working on how to make a perfect modern calendar, which can easily indicate the solar, lunar and sidereal dates and times of Planet Earth without scurrying for additional calendars, panchangs, ephemeris, calculators and more. Meanwhile, if one does decide to finally switch over to an International Fixed Calendar, the perfect day is 1 January 2024 (about 5 years from today). Its a Monday on all contemporary calendars!