The days of our lives are numbered

In the Gregorian calendar, today (or yesterday, if you are in certain parts of the world) is (or was) the first day of July in the Year Of Our Lord 2018, also called AD 2018 (Anno Domini, Latin for Year Of Our Lord) or 2018 CE (Common Era or Christian Era, take your pick) as opposed to BCE (Before the Common or Christian Era, ditto).

Note to self: Try to stop using so many parentheses.

There are other calendars, almost too many to mention, which has never stopped me before, but like Edith Bunker of old, I will stifle myself, except to mention in passing that AD 2018 is also the year AH 1439 (Anno Hijri) in the Islamic calendar and AM 5778 (Anno Mundi) in the Hebrew calendar. AH 1 coincided with AD 622, but do note, won't you, that although only 1396 years (2018 minus 622) have passed in the Christian calendar, 1439 years have passed in the Islamic calendar, because the Islamic year, being lunar, is consistently shorter by about 11 days than the solar year used by the Gregorian calendar. The Islamic years are slowly gaining on the Gregorian years, but it will be many years before the two coincide. According to what I read, the first day of the 5th month of CE 20874 in the Gregorian calendar will also be (approximately) the first day of the 5th month of AH 20874 of the Islamic calendar. I kid you not.

But I don't want to talk about calendars today. I want to talk about numeral systems.

There are many of those, too. Here are some of the most common ones:

A couple of those look familiar, but only a couple. From top to bottom, they are Arabic numerals, Eastern Arabic numerals, Roman numerals, Bengali-Assamese numerals, Malayalam numerals, Thai numerals, and Chinese numerals.

Here are the Babylonian numerals (written, of course, in cuneiform):

On this day in AD 1646, Gottfried Wilhelm Leibniz was born.

(Portrait of Gottfried Wilhelm Leibniz, c.1695 by Bernhard Christoph Francke. Hangs in the Herzog Anton Ulrich Museum, Braunschweig)

I'm sure your head, if it is anything like my head, is spinning. We'll stop now and talk more later.