I thought I should celebrate the once-in-a-century fact that all of our time/date digits are the same this morning by actually writing another post within a week of the last one (something I don’t think I’ve yet managed on this blog). Of course, the pedants among you might think it improper not to include the “20” in “2011”, but if we were to include those two digits then this occurrence will only ever have happened once before – on this day in 1111 – and will never happen again! Which is a bit upsetting.

Here is a question for you: what day of the week will it be the next time this happens, on 11/11/2111? This is the precisely the kind of question that some “idiot savants” are famously good at answering very quickly. How could they possibly do this, in their heads, in a matter of seconds? It seems very mysterious, until you give it some thought. Not that I have! But John Conway, a highly esteemed mathematician who needs no introduction to any other mathematicians who may be reading this (non-mathematicians might possibly unwittingly know of him through his creation the Game of Life…if you can remember back to the dark old days of Windows 95, this was actually included as a “game” along with Minesweeper et al.)^{*}, has actually invented a method of giving the day of the week on any given date. Why? I don’t know. Perhaps he was bored of competing with mere mortals and decided to take on the savants.