On Thu 2012-04-12T12:33:03 -0700, Steve Allen hath writ: > I offer this challenge: > > What was the second longest year in recorded history, and how many > leap seconds did it have?
Clearly the longest year in any contemporary calendar will fall into the category of one of the luni-solar calendar schemes where either the conventional or observational moon may dictate the insertion of an intercalary month. The reconstruction of what years may have had what lengths involves sifting through large amounts of data which are more complex than the tz database of zoneinfo. calendar year type mean solar seconds 365 day year 31536000 leap year 31622400 Sweden 1712 31708800 In my reckoning the 367 day year that Sweden had in 1712 is a mistake or aberration that does not deserve credit in this contest. The same goes for all pre-Julian years when the Roman calendar was subject to the whim of the officials. When various jurisdictions jumped from Julian to Gregorian they all had shorter years. Referring to zoneinfo again, there may be jurisdictions in which a leap year also contained the abandonment of daylight saving time, so those may be longer by an hour (or two). Similar shenanigans exist for jurisdictions which have declared themselves on the other side of the international date line, but most of those have shortened the calendar year. I want to restrict the scope to calendars issued by agents who imagined their jurisdiction extended to most of the world. Starting in 1972 the reckoning of calendar years according to international agreement used the new kind of second, but national laws did not immediately follow suit. In particular, federal law in the USA did not recognize leap seconds until 2007. calendar year seconds of TAI seconds in USA 1972 31622402 31622400 1976,1992 31622401 31622400 2008,2012 31622401 31622401 If the contest is based not on seconds counted according to some existing legal convention but rather on elapsed seconds of a constant length there is a different answer. It becomes necessary to refer to the tables of Delta T produced by Morrison and Stephenson, based on their research into historical eclipses and occultations. Around the beginning of the 20th century the rotation of the earth showed some huge decadal variations. calendar year Delta T change seconds of ET/TT 1908 (leap) 1.38 31622401.38 1909 1.33 31536001.33 1910 1.07 31536001.07 1911 1.83 31536001.83 1912 (leap) 1.29 31622401.29 1913 1.36 31536001.36 1914 1.19 31536001.19 1972 (leap) 1.141 31622401.141 It is amusing to look at the Length of Day values over history. In 1956, during the campaign where USNO and NPL were collaborating to establish the number of cesium oscillations in one ephemeris second, earth rotation decelerated a lot. In 1970, almost during the CCIR plenipotentiary that decreed radio broadcast time signals should use atomic seconds with leaps, earth rotation decelerated a lot. The changes in Delta T indicate that around 1910 the earth's crust was rotating slower than at any other time in history, even slower than it was in 1972 when the first leap seconds had to be inserted. Since 1972 the rotation of the earth's crust has accelerated, so calendar years have been shorter if measured in seconds of ET/TT/TAI. Of all calendar years above, the 2nd longest one in history was the year 1908, for it had a duration of 31622401.38 (ET/TT) seconds. -- Steve Allen <[email protected]> WGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
