Wednesday, June 17, 2015

The Month With 19 Days

If you had a really old calendar, you would run across a month that really looks weird.

      September 1752
Su Mo Tu We Th Fr Sa
       1  2 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30

The strange appearance reflects the change from the Julian to the Gregorian calendar we use today.

The old style Julian calendar was established by Julius Caesar in 45 B.C. to fix the Roman republican calendar (reckoned from the founding of Rome). Caesar, advised by Sosigenes, made the new calendar solar, not lunar. The length of the solar year was estimated at 365.25 days which was off by about 11 minutes. It's this 11 minutes that caused the problems with the Julian calendar.

By 1582, the cumulative effect of 11 minutes error has shifted the dates of the seasons by 13 days from Caesar's time. Pope Gregory XIII's reform reclaimed only 11 of the lost 13 days so that the date of the vernal equinox was restored to March 21, the date it had at the time of the Council of Nicaea, 325 A.D. With this reform we have fewer leap years too. In general, as before, every fourth year is leap except for those that are divisible by 100 but not by 400. So, for example, 1996 and 2000 are leap whereas 1900 and 2100 are not. The fact is, however, that, if all years divisible by 4,000 are denied their exceptional leap status, we would get even better conformity with actual time measurements. So far, no decision has been made to this effect. There is time yet.

 The new dating system was proclaimed in 1582 by Pope Gregory XIII. Those countries where the change has been accepted immediately (the Italian states, Portugal, Spain, 1582; the catholic German states, 1583), the day following October 4, was reckoned as October 15. (As a matter of fact, St. Theresa of Àvila died during the night between the 4th and 15th of October 1582.) Protestant German states adopted the new calendar in 1699; England and its colonies in 1752 (which explains the September 1752's anomaly); Sweden in 1753; Japan in 1783; China in 1912; Russia in 1918, Greece in 1923.

If ever asked: What's better, the Sun or the Moon? -
reply: The Moon. For the Sun only shines during daytime
when it's light anyway whereas the Moon shines at night.
Kozma Prutkov

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