The article says that the Gregorian leapyear system is designed to synchronize the calendar year with the mean tropical year. That isn't correct.
The Gregorian leapyear system was intended to synchronize the calendar year with the tropical year measured from one vernal equinox to the next.
The 365.2425 day average length of the Gregorian year, with the Gregorian leapyear system, most closely matches the tropical year measured from one vernal equinox to the next...which is 365.242374
The length of the mean tropical year, as of 2000, is about 365.24219 days...which is farther from 365.2422 than is the vernal equinox tropical year of 365.242374
To summarize the various year-lengths:
Gregorian year: 365.2425
Mean tropical year: 365.24219 diff from Gregorian: .00031
Vernal equinox tropical year: 365.242374 diff from Gregorian: .000126
Michael Ossipoff
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