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<p>[QUOTE="Dougmeister, post: 2361398, member: 56842"]Saw this on 'Astronomy Picture of the Day' (one of my daily stops on the Internet).</p><p><br /></p><blockquote><p><font size="3"><i>Today, February 29th, is a <a href="http://scienceworld.wolfram.com/astronomy/LeapDay.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://scienceworld.wolfram.com/astronomy/LeapDay.html" rel="nofollow">leap day</a> - a relatively rare occurrence. In 46 BC, <a href="https://en.wikipedia.org/wiki/Julius_Caesar" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Julius_Caesar" rel="nofollow">Julius Caesar</a>, featured here in a self-decreed minted coin, created a calendar system that added one <a href="http://scienceworld.wolfram.com/astronomy/LeapYear.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://scienceworld.wolfram.com/astronomy/LeapYear.html" rel="nofollow">leap day</a> every four years. Acting on advice by <a href="http://www.ics.forth.gr/~vsiris/ancient_greeks/hellinistic_period.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.ics.forth.gr/~vsiris/ancient_greeks/hellinistic_period.html" rel="nofollow">Alexandrian</a> astronomer <a href="https://en.wikipedia.org/wiki/Sosigenes_of_Alexandria" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Sosigenes_of_Alexandria" rel="nofollow">Sosigenes</a>, Caesar did this to make up for the fact that the Earth's year is slightly more than 365 days. In modern terms, the time it takes for the <a href="http://apod.nasa.gov/apod/ap990131.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://apod.nasa.gov/apod/ap990131.html" rel="nofollow">Earth</a> to circle the <a href="http://apod.nasa.gov/apod/ap000110.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://apod.nasa.gov/apod/ap000110.html" rel="nofollow">Sun</a> is slightly more than the time it takes for the <a href="http://apod.nasa.gov/apod/ap140319.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://apod.nasa.gov/apod/ap140319.html" rel="nofollow">Earth to rotate</a> 365 times (with respect to the Sun -- actually we now know this takes about 365.24219 rotations). So, if calendar years contained 365 days they would drift from the actual year by about 1 day every 4 years. Eventually July (named posthumously for <a href="http://www.literaturepage.com/read/shakespeare_juliuscaesar.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.literaturepage.com/read/shakespeare_juliuscaesar.html" rel="nofollow">Julius Caesar</a> himself) would occur during the northern hemisphere winter! By adopting a leap year with an extra day every four years, the <a href="http://www2.jpl.nasa.gov/calendar/" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www2.jpl.nasa.gov/calendar/" rel="nofollow">calendar year</a> would drift much less. This <a href="https://en.wikipedia.org/wiki/Julian_calendar" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://en.wikipedia.org/wiki/Julian_calendar" rel="nofollow">Julian Calendar</a> system was used until the year 1582 when <a href="http://www.newadvent.org/cathen/07001b.htm" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.newadvent.org/cathen/07001b.htm" rel="nofollow">Pope Gregory XIII</a> provided further fine-tuning when he added that leap days should not occur in years ending in "00", unless divisible by 400. This <a href="http://galileo.rice.edu/chron/gregorian.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://galileo.rice.edu/chron/gregorian.html" rel="nofollow">Gregorian Calendar</a> system is the one in common use today.</i></font></p><p><font size="3"><br /></font></p><p><font size="3"><i>[ATTACH=full]481730[/ATTACH] </i></font></p></blockquote><p>[/QUOTE]</p><p><br /></p>
[QUOTE="Dougmeister, post: 2361398, member: 56842"]Saw this on 'Astronomy Picture of the Day' (one of my daily stops on the Internet). [INDENT][SIZE=3][I]Today, February 29th, is a [URL='http://scienceworld.wolfram.com/astronomy/LeapDay.html']leap day[/URL] - a relatively rare occurrence. In 46 BC, [URL='https://en.wikipedia.org/wiki/Julius_Caesar']Julius Caesar[/URL], featured here in a self-decreed minted coin, created a calendar system that added one [URL='http://scienceworld.wolfram.com/astronomy/LeapYear.html']leap day[/URL] every four years. Acting on advice by [URL='http://www.ics.forth.gr/~vsiris/ancient_greeks/hellinistic_period.html']Alexandrian[/URL] astronomer [URL='https://en.wikipedia.org/wiki/Sosigenes_of_Alexandria']Sosigenes[/URL], Caesar did this to make up for the fact that the Earth's year is slightly more than 365 days. In modern terms, the time it takes for the [URL='http://apod.nasa.gov/apod/ap990131.html']Earth[/URL] to circle the [URL='http://apod.nasa.gov/apod/ap000110.html']Sun[/URL] is slightly more than the time it takes for the [URL='http://apod.nasa.gov/apod/ap140319.html']Earth to rotate[/URL] 365 times (with respect to the Sun -- actually we now know this takes about 365.24219 rotations). So, if calendar years contained 365 days they would drift from the actual year by about 1 day every 4 years. Eventually July (named posthumously for [URL='http://www.literaturepage.com/read/shakespeare_juliuscaesar.html']Julius Caesar[/URL] himself) would occur during the northern hemisphere winter! By adopting a leap year with an extra day every four years, the [URL='http://www2.jpl.nasa.gov/calendar/']calendar year[/URL] would drift much less. This [URL='https://en.wikipedia.org/wiki/Julian_calendar']Julian Calendar[/URL] system was used until the year 1582 when [URL='http://www.newadvent.org/cathen/07001b.htm']Pope Gregory XIII[/URL] provided further fine-tuning when he added that leap days should not occur in years ending in "00", unless divisible by 400. This [URL='http://galileo.rice.edu/chron/gregorian.html']Gregorian Calendar[/URL] system is the one in common use today.[/I] [I][/I] [I][ATTACH=full]481730[/ATTACH] [/I][/SIZE][/INDENT][/QUOTE]
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