The article doesn't contain explanations, so I dug into a few especially surprising ones:<p>---<p>> 7. Months have either 28, 29, 30, or 31 days.<p>Great Britain skipped from Sept 2, 1752 straight to Sept 14 when they switched from the Julian to the Gregorian calendar. Google "English calendar riots".<p>---<p>> 15. Unix time is the number of seconds since Jan 1st 1970.<p>When flipping over to the next second, Unix time "rewinds" back a second (i.e. repeats the last one) for leap seconds. [1]<p>---<p>> 73. Time passes at the same speed on top of a mountain and at the bottom of a valley.<p>This is from "time dilation", related to Einstein's General Relativity. In short, gravity warps spacetime.<p>Say you use a stopwatch to measure 1 Earth rotation (a "day"). For each extra km of altitude, the stopwatch will tell you it took ~10 extra nanoseconds to complete the trip around the Earth. [2]<p>---<p>[1] <a href="https://en.wikipedia.org/wiki/Unix_time#Leap_seconds" rel="nofollow">https://en.wikipedia.org/wiki/Unix_time#Leap_seconds</a><p>[2] <a href="https://en.wikipedia.org/wiki/Time_dilation#Time_dilation_caused_by_gravity_or_acceleration" rel="nofollow">https://en.wikipedia.org/wiki/Time_dilation#Time_dilation_ca...</a>