In the previous post, We found in MS-Excel, the date 1900/1/1 could be converted to the number “1”, and the dates after is to the number counted from that.
For exameple, 1900/1/2 is to “2”, 1900/1/3 is to “3”….

And “1901/1/1” was converted to “367” by the automatic converting system.


So was the year 1900 a leap year?
I was shocked to know it wasn’t.

Below is what I learned later:
It was a man-made rule for the ongoing calendar, in order to fit arithmetic rule to the astronomic event.
And MS-Excel doesn’t know it.(Year 1900 problem explained in Wikipedia)

To eliminate this problem, one can set the lower limit of the date to be the year 1904, which is a leap year.

Mac’s “Excel Preferences”…


“Count from the year 1904”

Then you would be able to handle all dates from 1904/1/1 without errors. In this system, the date 1904/1/1 is counted as “0”.

How complicated to handle dates and calendar in computer!…On the other hand, it means “The history of human being is far beyond computing.”… “Personal” computing, though.


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