lew (05/19/82)
The tropical (seasonal) year was 365.24219878 days long in 1900 and is shortening at a rate of .00000614 days per century (ref. Am.Eph. and Naut. Al.) The gregorian year is 365.2425 days long. With the proposed modification, it would be 365.24225 days long, but in 20,000 years the tropical year will have shortened to 365.24097 days. Note that by making all centuries common years, the year would be 365.24 days, so in 20,000 AD they might consider this modification. Additionally, the day is getting longer! ( The above calculations are based on "ephemeris days" which are set constant.) I believe the "leap seconds" are adjustments to day length, but I'm not sure. Actually the day length flucuates quite a bit, but the long term effect is a lengthening of .001 sec per century (ref. World Al. 1981) Note that this compounds the effect of the shortening year. To compare the magnitude of the effects, the day is lengthening by 10 ppb and the year shortening by 16 ppb. There is an article on the Gregorian calendar in the May 1982 SciAm. The author notes that scholars "consistently ignore" the shortening of the year, but he ignores the lengthening day as well. A final note, I read in an astronomy text somewhere that the russians have a different calendar that is more accurate than the gregorian, but won't diverge from it for a thousand years or so. Lew Mammel, Jr -BTL Indian Hill