Enigma 1685: A noted eccentric
15 February 2012
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From New Scientist #2852, 18th February 2012 [link]
My whimsical uncle tells me that he goes to his study at a certain time every day, but doesn’t say when. On Sundays when he arrives, he winds each of his two eight-day clocks and sets them to the correct time. One of the clocks gains an exact number of minutes each day, and the other loses the same, so the mean of the times is correct through the week.
He also tells me that on three days during a previous week (Sundays being excluded), as he entered the study he jotted down the time from one or other of the clocks, and he now produces the resulting slips of paper with the times 8:56, 9:11 and 9:20 written on them. These times are not necessarily in the order in which they were written down, nor do we know which clock is associated with which timing. Nevertheless, my uncle tells me I can deduce that he noted the time on a particular day of the week.
Which day was that?