{"id":36539,"date":"2024-05-04T02:37:00","date_gmt":"2024-05-04T02:37:00","guid":{"rendered":"https:\/\/www.lifeandnews.com\/articles\/?p=36539"},"modified":"2024-05-05T22:46:12","modified_gmt":"2024-05-05T22:46:12","slug":"why-does-a-leap-year-have-366-days","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/why-does-a-leap-year-have-366-days\/","title":{"rendered":"Why does a leap year have 366\u00a0days?"},"content":{"rendered":"\n

Bhagya Subrayan<\/a>, Purdue University<\/a><\/em><\/p>\n\n\n\n

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Curious Kids<\/a> is a series for children of all ages. If you have a question you\u2019d like an expert to answer, send it to curiouskidsus@theconversation.com<\/a>.<\/em><\/p>\n\n\n\n

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Why does a leap year have 366 days? Does the Earth move slower every four years? \u2013 Aarush, age 8, Milpitas, California<\/p><\/blockquote>\n\n\n\n

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You may be used to hearing that it takes the Earth 365 days to make a full lap, but that journey actually lasts about 365 and a quarter days. Leap years help to keep the 12-month calendar matched up with Earth\u2019s movement around the Sun.<\/p>\n\n\n\n

After four years, those leftover hours add up to a whole day. In a leap year, we add this extra day to the month of February, making it 29 days long instead of the usual 28.<\/p>\n\n\n\n

The idea of an annual catch-up dates back to ancient Rome, where people had a calendar with 355 days instead of 365 because it was based on cycles and phases of the Moon. They noticed that their calendar was getting out of sync with the seasons, so they began adding an extra month, which they called Mercedonius<\/a>, every two years to catch up with the missing days.<\/p>\n\n\n\n

In the year 45 B.C.E., Roman emperor Julius Caesar introduced a solar calendar, based on one developed in Egypt. Every four years, February received an extra day to keep the calendar in line with the Earth\u2019s journey around the Sun. In honor of Caesar, this system is still known as the Julian calendar.<\/p>\n\n\n\n

But that wasn\u2019t the last tweak. As time went on, people realized that the Earth\u2019s journey wasn\u2019t exactly 365.25 days \u2013 it actually took 365.24219 days<\/a>, which is about 11 minutes less. So adding a whole day every four years was actually a little more correction than was needed.<\/p>\n\n\n\n

In 1582, Pope Gregory XIII signed an order that made a small adjustment. There would still be a leap year every four years, except in \u201ccentury\u201d years \u2013 years divisible by 100, like 1700 or 2100 \u2013 unless they were also divisible by 400. It might sound a bit like a puzzle, but this adjustment made the calendar even more accurate<\/a> \u2013 and from that point on, it was known as the Gregorian calendar.<\/p>\n\n\n\n

What if we didn\u2019t have leap years?<\/h2>\n\n\n\n

If the calendar didn\u2019t make that small correction every four years, it would gradually fall out of alignment with the seasons. Over centuries, this could lead to the solstices and equinoxes<\/a> occurring at different times than expected. Winter weather might develop in what the calendar showed as summer, and farmers could become confused about when to plant their seeds. https:\/\/www.youtube.com\/embed\/YTOr8_ILqGw?wmode=transparent&start=0 Without leap years, our calendar would gradually become disconnected from the seasons.<\/p>\n\n\n\n

Other calendars around the world have their own ways of keeping time. The Jewish calendar, which is regulated by both the Moon and the Sun<\/a>, is like a big puzzle with a 19-year cycle. Every now and then, it adds a leap month to make sure that special celebrations happen at just the right time.<\/p>\n\n\n\n

The Islamic calendar<\/a> is even more unique. It follows the phases of the Moon<\/a> and doesn\u2019t add extra days. Since a lunar year is only about 355 days long, key dates on the Islamic calendar move 10 to 11 days earlier each year on the solar calendar.<\/p>\n\n\n\n

For example, Ramadan, the Islamic month of fasting<\/a>, falls in the ninth month of the Islamic calendar. In 2024, it will run from March 11 to April 9; in 2025, it will occur from March 1-29; and in 2026, it will be celebrated from Feb. 18 to March 19.<\/p>\n\n\n\n

Learning from the planets<\/h2>\n\n\n\n

Astronomy originated as a way to make sense of our daily lives, linking the events around us to celestial phenomena. The concept of leap years exemplifies how, from early ages, humans found order in conditions that seemed chaotic.<\/p>\n\n\n\n

Simple, unsophisticated but effective tools, born from creative ideas of ancient astronomers and visionaries, provided the first glimpses into understanding the nature that envelops us. Some ancient methods<\/a>, such as astrometry and lists of astronomical objects<\/a>, persist even today, revealing the timeless essence of our quest to understand nature.<\/p>\n\n\n\n

\"Photograph<\/a>
Ancient Egyptians were dedicated astronomers. This section from the ceiling of the tomb of Senenmut, a high court official in Egypt, was drawn sometime circa 1479\u20131458 B.C.E. It shows constellations, protective gods and 24 segmented wheels for the hours of the day and the months of the year. NebMaatRa\/Wikimedia<\/a>, CC BY<\/a><\/figcaption><\/figure>\n\n\n\n

People who do research in physics and astronomy, the field that I study<\/a>, are inherently curious about the workings of the universe and our origins. This work is exciting, and also extremely humbling; it constantly shows that in the grand scheme, our lives occupy a mere second in the vast expanse of space and time \u2013 even in leap years when we add that extra day.<\/p>\n\n\n\n

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Hello, curious kids! Do you have a question you\u2019d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com<\/a>. Please tell us your name, age and the city where you live.<\/em><\/p>\n\n\n\n

And since curiosity has no age limit \u2013 adults, let us know what you\u2019re wondering, too. We won\u2019t be able to answer every question, but we will do our best.<\/em><\/p>\n\n\n\n

Bhagya Subrayan<\/a>, PhD Student in Physics and Astronomy, Purdue University<\/a><\/em><\/p>\n\n\n\n

This article is republished from The Conversation<\/a> under a Creative Commons license. Read the original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Bhagya Subrayan, Purdue University Curious Kids is a series for children of all ages. If you have a question you\u2019d like an expert to answer, send it to curiouskidsus@theconversation.com. Why does a leap year have 366 days? Does the Earth move slower every four years? \u2013 Aarush, age 8, Milpitas, California You may be used […]<\/p>\n","protected":false},"author":44,"featured_media":36540,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1862],"tags":[218,15241,6689,6786,15239,15240,15238,1103,11936,4687,2913,3621],"_links":{"self":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/36539"}],"collection":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/users\/44"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/comments?post=36539"}],"version-history":[{"count":2,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/36539\/revisions"}],"predecessor-version":[{"id":36555,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/36539\/revisions\/36555"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media\/36540"}],"wp:attachment":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media?parent=36539"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/categories?post=36539"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/tags?post=36539"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}