Arab Calendar Cannot Tell Time

I first wrote about this in the 1990s. I have repeated it a few times since. Then today this thing popped up about the year 2020 and 1964. 

The modern calendar ie the Gregorian Calendar is seeing a phenomena whereby this year 2020 (a leap year) is also an exact duplicate of the year 1964 (also a leap year).

If today is Thursday 16th January, 2020 so it was 56 years ago in 1964. 16th January was also a Thursday in 1964. In the Gregorian calendar this year is an exact duplicate of 1964.  Saturday February 29th is common to both years.  

You can read something about this calendar event here : 

https://www.timeanddate.com/calendar/?year=1964&country=69

That article also showed the list of Public Holidays in Malaysia in 1964. Here it is :

This appears to be a mix of State and Federal Holidays. Well Deepavali is not listed as a Public Holiday in 1964. Or Wesak Day. The Sultan's birthdays are also not mentioned. 

The thing that caught my attention were the Islamic holidays. In 1964 the Hari Raya Puasa was on 15th February. The puasa began on 16th January (ie today). 

Herein lies the usefulness of the Gregorian Calendar and the reason why the Arabic calendar is "pegged" to the Gregorian Calendar. The Arabic calendar cannot tell time. That is why the modern Arabic calendar is pegged to the Gregorian Calendar. 

Being a solar calendar the Gregorian calendar is very precise. The rotation of the earth around the sun and the wobble of the earth about its own axis (the 23.5 degree tilt) etc are known and measurable and can give precise reckoning of the Erath's position in space. Which is what the annual calendar tells us.

Farmers must know when the rains will come. 

Winter clothing manufacturers must know when it is going to get cold in New Zealand.  

All this depends on the position of the Earth around the sun. The Gregorian calendar and some other calendars like the Chinese and Tamil calendars capture this quite well.

Just like the Tamil Ponggal the Chinese New Year is also a harvest festival. By the way Ponggal means 'the boiling'. It refers to boiling the first rice from the harvest.

And since rice is harvested around the same time in India and China, Chinese New Year always appears from late January to mid February (in the Gregorian Calendar). These are predictable annual events. 

Back to Hari Raya Puasa in 1964 - it fell on 15th February 1964. 

In the Arabic calendar Hari Raya Puasa falls on the 1st day of the Arabic month of Syawal. So in 1964 the Arabic 1st of Syawwal fell on 15th February (of the Gregorian calendar).

But not this year. This year 2020 the Arabic 1st of Syawal aka Hari Raya Puasa will fall  on 24th May 2020.

So the Arabic calendar cannot be used to tell time. 

It must be pegged to another calendar like the Gregorian, Chinese or Tamil calendar.