PLANETARY YEARS, the periods of time in which the
several planets make their revolutions round the sun or
earth.—As from the proper revolution of the sun, the
solar year takes its original; so from the proper revo-
lutions of the rest of the planets about the earth, so
many sorts of years do arise, viz. the Saturnian year,
which is defined by 29 Egyptian years, 174 hours, 58
minutes, equivalent in a round number to 30 solar
years.—The Jovial year, containing 317 days, 14
hours, 59 minutes.—The Martial year, containing 321
days, 23 hours, 31 minutes.—For Venus and Mer-
cury, as their years, when judged of with regard to
the earth, are almost equal to the solar year; they are
more usually estimated from the sun, the true centre
of their motions: in which case, the former is equal
to 224 days, 16 hours, 40 minutes; the latter to 87
days, 23 hours, 14 minutes.