ENOSUCHBLOG Programming, philosophy, pedaling. Home Tags Series Favorites Archive Main Site TILs Jun 9, 2015     Tags: programming     This post is at least a year old. Calendars and Missing Dates # In 1582, under the inter gravissimas papal bull, the Catholic world transitioned from the Julian Calendar to the Gregorian Calendar . This new calendar shortened the length of the year from 365.25 days to 365.2425 , a reduction of just 0.002% . One side effect of this is the modern leap year system, in which every fourth and 400th year is a leap year, but no other year divisible by 100 is. For example, this means that 1900 was a normal year, 1904 was a leap year, and 2000 was also a leap year. Another side effect (and the topic of today’s post) was that the Julian and Gregorian calendars no longer agreed on the date. Calculating each from 1 to to 1582 AD, the Julian calendar had slowly accumulated “drift” relative to the Gregorian calendar, lagging eleven days behind it.…