In general, a calendar divides time and grouped into different periods or intervals. The Gregorian calendar was the result of following the stars, parallel to the mathematical development that combines cultural traditions inherited or imposed, and adjustments made for its completion.
Over the years, achieved a better accuracy in the calculation of length of the year and consequently the defects of the Julian calendar. In 1582 Pope Gregory XIII appointed the Italian astronomer Christopher Clavius, working on calendar reform, specifically with regard to leap years, since the time of year is not exactly 365.25 days, but 365 days 5 hours 49 minutes and 16 seconds, according to the astronomical tables prepared by the Academy of Toledo in the thirteenth century, by express order of Alfonso X the Wise (1221-1284), king of Castile and Leon. (Today we know with more precisely, that the duration of the year is 365 days, 5 hours, 48 \u200b\u200bminutes and 46.15 seconds)
line with the recommendations of Clavius, Pope Gregory XIII decreed that:
- will leap that year whose number is divisible by 4, except the secular year, multiples of 100, which will be leap years only if divisible by 400. (For example, 1900 was not a leap year, 2000 does what it was, but by 2100 will not be)
- As from the effective date of the Julian calendar had been considered as leap years should not be and had already an accumulated error of 10 days, would be removed 10 days to the calendar: the day following October 4, 1582 (the feast of St. Francis of Assisi) would be called to be 15 October (this year is the year 1582 shortest Christianity, with 355 days, and days 5 to 14 October of that year did not exist).
According to astronomical studies, the timing is advanced a little to the Sun, each year he wins 26 seconds, which equates to one day every 3323 years. Thus, it is likely that you lost a day when the year 4000. For this small difference has been established additional rules , Which is that multiples of 4000 years are not leap years. Finally, these rules are mentioned, they define who is known as Gregorian calendar.
Finally, and always related to the issue of correcting the deficiencies that could generate the shape of measuring time, remember that the number of seconds in a day is 60 x 60 x 24 = 86400, during each day of week, and during each week of the year.
is known that the tides are the product of the gravitational force exerted by the Moon on Earth, this effect is greater on the part of Earth that is opposite in the opposite side. The result of this effect is small lengthening of the Earth in the direction of the Moon, which has a greater effect on the liquid mass of the solid part, this occurs twice a day the tides . Water bodies produce friction with the lower parts of the sea, and this friction transforms the energy into heat, ie the Earth is losing rotational energy.
As clearly explained Isaac Asimov, loss of turnover is not easily noticed, but to astronomers this means that a star observed in a position in a given time, there is now a significant shift , the same applies to the eclipses. When the rotation Earth is 0.9 seconds behind in adding a leap second to make the planet is in sync again, which is useful and necessary for navigation, for telecommunications and for astronomy.
was created in 1972 resynchronization system on the planet, at that time were added 10 seconds to make the adjustment, ie, a curious fact, the longest year of our era is 1972 in addition to being a leap year, is I added 10 seconds. Since 1972 until now they have added a total of 33 of these second, known as Leap always late June to late December, the second youngest of them in 1998 and 31 December 2005 Added the last of them.
For more details on this subject, I recommend the article "Of Time and the Calendars where plenty of useful information and answers to questions such as: What is a day and what a year? , What has been the longest year and what the shortest of our era, that is, after Christ, and also what year was 445 days?, why, in Russia, the so-called October Revolution of 1917 held in November?, why the present order of the seven days of the week?, Why October is not the eighth month and September is the seventh month as the name suggests?, Why February has 28 days, What fact or significant event occurred on October 7, 1582 in Italy? , what year was Jesus Christ? among others.
"- So now that the planet makes one revolution every minute
I have not a second of rest.
- It's strange, last day here a minute!
- It is strange, "said the lamplighter. A month ago and we chatted.
- A month?
- Yes, thirty minutes. Thirty days! Good night, "repeated the lamplighter."
The Prince
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