--- title: Autumn Equinox 2017: Why Friday Is the First Day of Fall description: The 2017 autumn equinox marks the first day of fall for anybody living in the Northern Hemisphere, meaning longer nights are coming canonical: https://time.com/4953059/autumn-equinox-2017-first-day-fall/ author: Melissa Chan article:opinion: false article:content_tier: free article:published_time: 2017-09-22T14:19:17.000Z article:modified_time: 2026-03-31T11:16:12.252Z article:section: Science og:title: The Autumn Equinox Is the First Day of Fall og:description: Shorter days and longer nights are coming og:url: https://time.com/4953059/autumn-equinox-2017-first-day-fall/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blte2c0c030f16a6970/6988dee8656a3f5537bd1cd5/gettyimages-850823642.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 6584 og:image:height: 3704 og:image:alt: 170922_fall og:type: article twitter:card: summary_large_image twitter:title: The Autumn Equinox Is the First Day of Fall twitter:description: Shorter days and longer nights are coming twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blte2c0c030f16a6970/6988dee8656a3f5537bd1cd5/gettyimages-850823642.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Autumn Equinox 2017: Why Friday Is the First Day of Fall > Sponsored content. 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It reaches 40,000 subscribers with a 34.2% open rate and a 2.1% click rate as of August 2026. #### Where can I follow the energy transition as a business story? Future Proof covers climate and energy as an economic and business story rather than only an environmental one. It publishes every Friday and is free at time.com/newsletters. #### Who writes Future Proof? Justin Worland, a senior correspondent at TIME and an award-winning climate journalist, writes Future Proof. #### Is Future Proof free? Yes. Future Proof is free at time.com/newsletters.  by [Melissa Chan](https://time.com/author/melissa-chan/)  ## Melissa Chan Sep 22, 2017 2:19 PM UTC  Top view woman on warm sweater holding hands cup cappuccino on wooden table. Autumn leaves and acorn Top view woman on warm sweater holding hands cup cappuccino on wooden table. Autumn leaves and acorn katiafonti—Getty Images  by [Melissa Chan](https://time.com/author/melissa-chan/)  ## Melissa Chan Sep 22, 2017 2:19 PM UTC Friday’s autumn equinox marks the end of summer and the first day of fall for anybody living in the Northern Hemisphere, meaning colder weather and longer nights are on the way. The 2017 autumn equinox, which signals the official change of season, occurs on Sept. 22 at 4:02 p.m. EDT, according to the [U.S. Naval Observatory](http://aa.usno.navy.mil/data/docs/EarthSeasons.php), which handles astronomical data and serves as the official source of time for the military and country. On the day of the [equinox](http://time.com/32042/equinox-first-day-of-spring-words/) — a Latin term that means equality between day and night — day and night are each 12 hours long, according to [NASA](https://www.nasa.gov/audience/forstudents/k-4/home/feature%5Fautumn.html). The U.S. space agency said equinoxes occur when the Earth is in alignment with the sun directly above the Earth’s equator. Seasons change based on how the Earth, which spins on a tilted axis, moves around the sun each year, NASA said. For example, it’s summer when the North Pole is pointed toward the sun, which provides the Northern Hemisphere with direct sunlight. But it’s winter when the North Pole is pointed away from the sun. For years, [Google](https://www.google.com/) has celebrated the astronomical event through Google Doodle illustrations. Friday’s image depicts a tiny scarf-wearing rodent happily hopping underground to sip a cup of tea. 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