{"673078":{"#nid":"673078","#data":{"type":"news","title":"Leap Years, Explained","body":[{"value":"\u003Cp\u003EThis year brings another February 29. Why do leap years occur? \u003Ca href=\u0022https:\/\/astronomy.gatech.edu\/Biographies.php\u0022\u003EJim Sowell\u003C\/a\u003E is a principal academic professional in the \u003Ca href=\u0022https:\/\/physics.gatech.edu\u0022\u003ESchool of Physics\u003C\/a\u003E and the director of the \u003Ca href=\u0022https:\/\/astronomy.gatech.edu\/\u0022\u003EGeorgia Tech Observatory\u003C\/a\u003E. He says the leap year\u2019s creation goes back to Julius Caesar.\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003EEvery four years, the addition of one day \u2013 that is, February 29 \u2013 brings us back closer to a more accurate location in the Earth\u2019s orbit with respect to the stars.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EGetting to our current calendar system has been a complicated process, mostly because of three important celestial motions: the Earth\u2019s spin (or rotation), which gives us the day; the orbit of the Earth around the Sun, which gives us the year; and the orbit of the Moon around the Earth, the basis for the month.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EDuring the reign of Julius Caesar (46 \u2013 44 B.C.), the Egyptians were some of the best astronomers. They could see that the Earth\u2019s orbit was very close to 365.25 days. Caesar used their knowledge to bring order to the Roman calendar. He established that every fourth year would be a leap year, tacking one day onto the last month \u2013 this is the basis of the Julian Calendar. Later, in 45 B.C., he moved the beginning of the year from March 1 to January 1. This is why the \u201cseventh\u201d month (September; Latin septem) through \u201ctenth\u201d month (December; Latin decim) are now the ninth through twelfth positions in the calendar. But before that move, the practice of adding the leap day at the end of the then year \u2013 February \u2013 had been established. (By the way, the month of July was later named for Julius Caesar after his death.)\u003C\/p\u003E\r\n\r\n\u003Cp\u003EIn the late 1500s, astronomers under Pope Gregory XIII (for whom the modern Gregorian Calendar is named) realized 365.25 days wasn\u2019t exactly right. The Earth\u2019s orbit is actually 365.242199 days long. After hundreds of years using the Julian Calendar, spring had begun moving into winter. The Catholic Church did not want the celebration of Easter to occur in the winter. The astronomers worked out a new formula to skip some leap days to stay closer to an exact measurement. Certain hundred-year dates are leap years, such as 2000, whereas others (2100) will not be leap years. The Catholic Church also took ten days out of the calendar in 1582 to get it more closely synced with respect to its orbital position and the stars: October 4, 1582, was followed by October 15, 1582. Later, the British Empire, in 1752, did the same calendar adjustment but had to remove eleven days.\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThe Gregorian Calendar will work for a long time \u2014 at least for the next 3,300 years before an extra day is needed. Then a new calculation must be derived to get our calendar corrected with the Earth\u2019s orbit. Today\u2019s astronomers aren\u2019t sure what that will be, but they\u2019ve decided to let future astronomers figure it out.\u003C\/p\u003E\r\n","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EThis year brings another February 29. Why do leap years occur? Jim Sowell is a principal academic professional in the School of Physics and the director of the Georgia Tech Observatory. He says the leap year\u2019s creation goes back to Julius Caesar.\u003C\/p\u003E\r\n","format":"limited_html"}],"field_summary_sentence":[{"value":"This year brings another February 29. Why do leap years occur?"}],"uid":"27469","created_gmt":"2024-02-20 17:07:02","changed_gmt":"2024-02-23 21:44:25","author":"Kristen Bailey","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2024-02-23T00:00:00-05:00","iso_date":"2024-02-23T00:00:00-05:00","tz":"America\/New_York"},"extras":[],"hg_media":{"635643":{"id":"635643","type":"image","title":"James Sowell, director of the Georgia Tech Observatory. Photo: Rob Felt","body":"\u003Cp\u003EJames Sowell, director of the Georgia Tech Observatory. Photo: Rob Felt\u003C\/p\u003E\r\n","created":"1590503966","gmt_created":"2020-05-26 14:39:26","changed":"1708704135","gmt_changed":"2024-02-23 16:02:15","alt":"James Sowell, director of the Georgia Tech Observatory. Photo: Rob Felt","file":{"fid":"241872","name":"James Sowell photo Rob Felt.jpg","image_path":"\/sites\/default\/files\/images\/James%20Sowell%20photo%20Rob%20Felt.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/James%20Sowell%20photo%20Rob%20Felt.jpg","mime":"image\/jpeg","size":430700,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/James%20Sowell%20photo%20Rob%20Felt.jpg?itok=-5PkV2Gu"}},"673196":{"id":"673196","type":"video","title":"Why We Have Leap Years ","body":"\u003Cp\u003E\u003Cspan\u003EWhy do leap years occur? Jim Sowell, a principal academic professional in the School of Physics and director of the Georgia Tech Observatory, explains the leap year\u2019s creation dates back to Julius Caesar.\u003C\/span\u003E\u003C\/p\u003E\r\n","created":"1708723163","gmt_created":"2024-02-23 21:19:23","changed":"1708723163","gmt_changed":"2024-02-23 21:19:23","video":{"youtube_id":"QnYgSsHm3Io","video_url":"https:\/\/www.youtube.com\/watch?v=QnYgSsHm3Io"}}},"media_ids":["635643","673196"],"related_links":[{"url":"https:\/\/astronomy.gatech.edu\/","title":"Astronomy at Georgia Tech"}],"groups":[{"id":"1278","name":"College of Sciences"},{"id":"1214","name":"News Room"},{"id":"126011","name":"School of Physics"}],"categories":[],"keywords":[],"core_research_areas":[],"news_room_topics":[{"id":"71871","name":"Campus and Community"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Ca href=\u0022mailto:kristen.bailey@comm.gatech.edu\u0022\u003EKristen Bailey\u003C\/a\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003EInstitute Communications\u003C\/p\u003E\r\n","format":"limited_html"}],"email":[],"slides":[],"orientation":[],"userdata":""}}}