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The Tropical Year Calendar

The Tropical Year Calendar Julian/Gregorian    The tropical year is the time, taken by the Sun, to pass from the vernal equinox to the vernal equinox. It equals 365 days, 5 hours, 48 minutes, and 46 seconds, or 365.2422 days. The tropical year is used, to keep track of seasons, planting, and harvesting. There is a need to create a calendar, with a whole number of days per year to accurately follow the tropical year without losing synchronization with the seasons over a period of time. We begin with a calendar of 365 days per year. Our calendar year is shorter than the tropical year by 0.2422 days. So to correct (approximately), we add 1 day every four years (leap year). Thus, three calendar years are 365 days long; the fourth calendar year is 366 days long. The average length of the calendar year in days now becomes (3 x 365 + 366)/4 = 365.25 days. This calendar system was actually instituted for use in the Roman Empire by Julius Caesar around 46 BC. But since the Julian calen...