406. The parts of time are Seconds, Minutes, Hours, Days, Years, Cycles, Ages, and Periods.
A Year.
407. The original standard, or integral measure of Time, is a year; which is determined by the Revolution of some Celestial Body in its Orbit, viz. the Sun or Moon.
Tropical Year.
408. The time measured by the Sun’s Revolution in the Ecliptic, from any Equinox or Solstice to the same again, is called the Solar or Tropical Year, which contains 365 days 5 hours 48 minutes 57 seconds; and is the only proper or natural year, because it always keeps the same seasons to the same months.
Sidereal year.
409. The quantity of time, measured by the Sun’s Revolution, as from any fixed Star to the same Star again, is called the Sidereal Year; which contains 365 days 6 hours 9 minutes 141⁄2 seconds; and is 20 minutes 171⁄2 seconds longer than the true Solar Year.
Lunar Year.
410. The time measured by twelve Revolutions of the Moon, from the Sun to the Sun again, is called the Lunar Year; it contains 354 days 8 hours 48 minutes 37 seconds; and is therefore 10 days 21 hours 0 minutes 20 seconds shorter than the Solar Year. This is the foundation of the Epact.
Civil Year.