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Credit & Copyright: Rune Rysstad
Explanation:
Today,
February 29th, is a
leap day - a relatively rare occurrence.
Advised by
Alexandrian astronomer Sosigenes,
Roman dictator
Julius Caesar, pictured above in a self-decreed minted coin,
created a
calender system
in 46 BC that contained one
leap day
every four years. The reason for adding
leap
days was that a year -
defined by the time it takes the Earth to circle the Sun - does not actually
take an exact integer number of days - defined by the time it takes for the
Earth to rotate once. In fact, one year by these
astronomical definitions is about 365.24219 days.
If all calendar years contained 365 days, they
would drift from the actual year by about 1 day every 4 years.
Eventually July (named posthumously for Julius Caesar himself)
would occur during the northern hemisphere winter!
By making
most years 365 days but every fourth year 366 days,
the calendar year and the actual year remained more nearly in step.
This "Julian" calender system was used until the year
1582 when
Pope Gregory
XIII added that leap days should not occur in years
ending in "00" except if divisible by 400, providing a further
fine tuning.
This "Gregorian" calender system
is the one in most common use today.
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A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
Publications with keywords: Julius Caesar - Leap Days
Publications with words: Julius Caesar - Leap Days
See also: