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class=po></div><div id=mpo></div><div id=anw class=alert-notice__wrap></div><div class=main-content-div><script> window.TAD=window.TAD||{};TAD.abtest='a'; </script><div class=bc__wrap><div class="row socrow"><div id=bc class="fixed"><div id=bct><a target=_top href="/" class=fx>Home</a>   <a target=_top href="/news/" class=fx>News</a>   <a target=_top href="/news/astronomy/" class=fx>Astronomy News</a>   Equal Day and Night? It Happens in June!</div></div></div></div><main class="article layout-grid layout-grid--article"><article class="layout-grid__main article__content"><h1 class=article__title>Equal Day and Night? It Happens in June!</h1><h4 class=article__sub-title></h4><p class=article__byline>By <a href='/company/team-editorial#kb'>Konstantin Bikos</a>. <span class=article__date><span title="June 14, 2024 or 2024-06-14">Published 14-Jun-2024</span><span title="September 22, 2024 or 2024-09-22">. Changed 22-Sep-2024</span></span><span class=article__rss><a class=rss href="https://rss.timeanddate.com/news-astronomy.rss"><img src="//c.tadst.com/gfx/rssfeed14.png" width=14 height=14 alt=RSS title="Click to subscribe to this news feed" border=0></a></span></p><p class=article__lead>Days and nights of equal length are normally associated with the equinoxes. But in some world regions, it happens around the solstices. Spoiler alert: It’s not at the equator.</p><div class=article__body><figure class="article__figure "><div class=article__img-container><img src="//c.tadst.com/gfx/600x337/guayaquil-chapel.jpg?1" width=600 height=337 alt="Panoramic sunset view of a hilltop church and cityscape, with colorful buildings, communication towers, and a large terrace overlooking the city." class=article__img srcset="//c.tadst.com/gfx/900x506/guayaquil-chapel.jpg?1 1.5x,//c.tadst.com/gfx/1200x675/guayaquil-chapel.jpg?1 2x"></div><figcaption><p class=article__img-caption>Guayaquil, Ecuador, is one of the places where day and night are equal at the June solstice.</p><p class=article__img-credit>©iStockphoto.com/AlanFalcony</p></figcaption></figure><p><a href="/astronomy/equinox-solstice.html" class="cw-link tad-link-explore">What are solstices and equinoxes? </a></p><h2>Guayaquil’s 12-Hour Solstice</h2><p>Every year, as people in the Northern Hemisphere celebrate the <a href="/calendar/summer-solstice.html">summer solstice</a>, marking the <strong>longest day</strong> of the year and the <a href="/calendar/summer-solstice.html">beginning of summer</a>, a select few will experience a period of <a href="/astronomy/equilux.html">equilux</a>, when <strong>day and night are equal</strong>.</p><p>One such place is the northern half of Ecuador’s most populous city, <a href="/worldclock/ecuador/guayaquil">Guayaquil</a>. Here, day and night reaches a <strong>near-perfect 12-hour equilibrium</strong> each day for four or five days over the June solstice. (The city center, a few kilometers farther south, has an equilux <a href="/sun/ecuador/guayaquil?month=6">a few weeks before</a> the June solstice, and again <a href="/sun/ecuador/guayaquil?month=7">a few weeks after</a>.)</p><h3>June Solstice Daylengths</h3><table class="table table--striped table--inner-borders-all"><tr><td><strong>Latitude</strong></td><td><strong>Daylength (hrs:min:sec)</strong></td></tr><tr><td>90 degrees north (North Pole) </td><td>24:00:00 </td></tr><tr><td>41 degrees north (New York) </td><td>15:05:38 </td></tr><tr><td>0 degrees (equator) </td><td>12:07:18 </td></tr><tr><td>2.1 degrees south (Guayaquil) </td><td>12:00:00 </td></tr><tr><td>90 degrees south (South Pole) </td><td>00:00:00 </td></tr></table><br><p>What may surprise you is that Guayaquil <strong>isn’t on the equator</strong> but about 240 km (150 mi) south of it.</p><p>For Ecuador’s capital, <a href="/worldclock/ecuador/quito">Quito</a>, which straddles the <a href="/geography/equator.html">equator</a>, the day of the June solstice lasts <a href="/sun/ecuador/quito?month=6">12 hours and 6 minutes</a>. In fact, Quito <strong>never experiences an equilux</strong>: each day of the year is longer than 12 hours.</p><p>Why is that so? Let’s find out.</p><h2>Space Geometry</h2><p>It’s one of those bits of folk wisdom you learn in school that starts to fall apart once you look at the fine print: that day and night are equal at the equinoxes.</p><p>After all, the word <em>equinox</em> is Latin for ‘equal night.’</p><p>Of course, there’s a kernel of truth to it. In late March and late September, the Sun is <a href="/astronomy/seasons-causes.html">right above the equator</a>, and Earth’s axis stands at a <strong>right angle to the Sun’s rays</strong>. Based on this simple fact of space geometry, every location on the Earth’s surface should get 12-hour days, right?</p><p><a href="/calendar/seasons.html" class="cw-link tad-link-explore">Solstice and equinox times down to the minute </a></p><h2>Refraction and Sun’s Size = Longer Days</h2><p>Wrong. For one, the claim refers to the <strong><em>geometric center</em></strong> of the Sun’s disk. But in reality, it has an angular size of about 0.5 degrees in the sky. A day begins and ends when its <strong><em>upper edge</em></strong> crosses the horizon, so the total length of day includes the time it takes for the upper half of the Sun to appear at sunrise and disappear at sunset.</p><p>Secondly, Earth's atmosphere causes <a href="/astronomy/refraction.html">refraction</a>, making the <strong>Sun appear slightly higher</strong> in the sky, further increasing daylength. (The extent of this distortion depends on air temperature and pressure.)</p><p>Both phenomena <strong>result in slightly longer days</strong>, and they are the reason why</p><ul><li>equinox days are slightly longer than 12 hours all around the globe, and</li><li>days close to the equator—including in Quito—are slightly longer than 12 hours all year round. </ul><figure class="article__figure article__figure--zoomable" data-tad-control=ClassOnClick data-tad-options="{classname: 'article__figure--zoomed'}"><div class=article__img-container><img src="//c.tadst.com/gfx/600x337/dates-of-equilux-map.png?1" width=600 height=337 alt="Dates of equilux at selected locations - world map." class=article__img srcset="//c.tadst.com/gfx/900x506/dates-of-equilux-map.png?1 1.5x,//c.tadst.com/gfx/1200x675/dates-of-equilux-map.png?1 2x"></div><div class=article__lightbox><img src="//c.tadst.com/gfx/1200x675/dates-of-equilux-map.png?1" width=1200 height=675 alt="Dates of equilux at selected locations - world map." class=article__img-large loading=lazy></div><figcaption><p class=article__img-caption>Graphic 1 (click to enlarge): Different latitudes experience the equilux on different dates. All locations have two equiluxes per year except in two cases: Locations around 2.1 degrees south and 2.2 degrees north have one equilux, and locations closer to the equator do not have any.</p><p class=article__img-credit>©timeanddate</p></figcaption></figure><h2>2.1 Degrees South: The Equilux Sweet Spot</h2><p>For the timeanddate.com <a href="/astronomy/">Astronomy</a> Team, this inspired the question: How far from the equator do equiluxes start to occur, and when do they happen?</p><p>Delving into our <a href="/sun/">Sun and daylength numbers</a> for June, we found that <strong>sweet spot</strong> in Guayaquil, more precisely, at <strong>2.1 degrees of southern latitude</strong>. (The <a href="/geography/longitude-latitude.html">longitude</a> is irrelevant here.)</p><p>All locations closer to the equator experience <strong>no equiluxes</strong>; locations farther south have <strong>two equiluxes</strong> per year—and they happen on very different dates, as shown in graphic 1.</p><p>In the temperate zones, the equilux happens <em>around</em>, but <strong>never <em>on</em> the date of the equinox</strong>. For example, the equiluxes in New York occur on <a href="/sun/usa/new-york?month=3">March 16 or 17</a> and <a href="/sun/usa/new-york?month=9">September 25 or 26</a>; in that time zone, the equinoxes fall on <a href="/calendar/seasons.html?n=179">March 19 or 20 and September 22 or 23</a> each year.</p><h2>A Perfect Balance</h2><p>So, how come the zone experiencing equiluxes in the <a href="/geography/southern-northern-hemisphere.html">Southern Hemisphere</a> begins at precisely 2.1 degrees of southern latitude?</p><p>Simply put, it’s the latitude where the <strong>day-shortening effects</strong> of <a href="/astronomy/axial-tilt-obliquity.html">Earth’s tilt</a> in June (<a href="/calendar/winter-solstice.html">southern winter</a>) and the cumulative <strong>day-lengthening effects</strong> of the Sun’s angular size and atmospheric refraction perfectly <strong>cancel each other out</strong> to produce 12-hour days at this time of the year.</p><p>Have a look at graphic 2 to see these effects in action from a top-down perspective:</p><ul><li>The Sun’s angular size and refraction cause the Sun’s light to reach slightly <strong><em>more</em> than half the globe</strong>. In the illustration, this is represented by the slightly blurred transition between night and day.</li><li>In June, the Southern Hemisphere is <strong>tilted <em>away</em></strong> from the Sun. At 2.1 degrees south, this effect shortens the day just as much as the above-mentioned factors lengthen it: As the graph shows, the line marking the “real” transition between day and night—the left edge of the blurred zone—crosses that latitude at exactly its <strong>halfway point</strong>.</li></ul><figure class="article__figure article__figure--zoomable" data-tad-control=ClassOnClick data-tad-options="{classname: 'article__figure--zoomed'}"><div class=article__img-container><img src="//c.tadst.com/gfx/600x337/equilux-explanation.png?1" width=600 height=337 alt="Illustration of the globe shoving equal day and night time at −2.1° latitude." class=article__img srcset="//c.tadst.com/gfx/900x506/equilux-explanation.png?1 1.5x,//c.tadst.com/gfx/1200x675/equilux-explanation.png?1 2x"></div><div class=article__lightbox><img src="//c.tadst.com/gfx/1200x675/equilux-explanation.png?1" width=1200 height=675 alt="Illustration of the globe shoving equal day and night time at −2.1° latitude." class=article__img-large loading=lazy></div><figcaption><p class=article__img-caption>Graphic 2: The Sun’s angular size and refraction cause the Sun’s rays to reach a bit more than half of the globe. At the June solstice, while locations at higher latitudes experience the longest day of the year, the vertical line marking the border between nighttime and the outermost reaches of direct sunlight divides the line at 2.1 degrees southern latitude into two halves of exactly equal length. Locations at that latitude experience an equilux.</p><p class=article__img-credit>©timeanddate</p></figcaption></figure><h2>Northern Equilux Farther from the Equator</h2><p>One of the fun facts that emerged during our deep dive into our Sun data—which took some additional detective work to figure out—is that the equilux sweet spot <strong>north of the equator</strong> is at a <strong>slightly higher latitude</strong> than in the Southern Hemisphere.</p><p>Here, the equilux zone starts <strong>closer to 2.2 degrees north</strong> (or, to be more precise, 2.17 degrees north). Locations on that latitude, such as <a href="/worldclock/malaysia/malacca-city">Malacca</a> in Malaysia, <a href="/sun/@2.16594,102.34960?month=12">experience equal day and night</a> on or around the <a href="/calendar/december-solstice.html">December solstice</a>, which marks the shortest day of the year and the beginning of winter in the Northern Hemisphere.</p><p>This very slight <strong>latitudinal difference</strong>, which only amounts to just over 7 kilometers (4 miles), is due to a very small change in the Sun’s angular size during the course of the year. “In December, Earth is a bit closer to the Sun, so the Sun is slightly <strong>larger in the sky</strong>,” explains <a href="/company/by/#graham">Graham Jones</a>, an astrophysicist at timeanddate.com.</p><p>“The effect of this tiny increase in the Sun’s angular size is that—all over the world—sunrise and sunset last a tiny bit longer. For the Northern Hemisphere, this means the <strong>minimum latitude</strong> at which an equilux can occur is a tiny bit further away from the equator.”</p></div></article><aside class="layout-grid__sidebar article__sidebar"><div class="clip-block clip-block--list"><div class=blk-series><h3 class="blk-series__title clip-block__title">The Science of Seasons</h3><ol class=blk-series__list><li class="blk-series__item "><a href="/astronomy/seasons-causes.html" class=blk-series__item-link> What Causes Seasons? </a></li><li class="blk-series__item "><a href="/astronomy/axial-tilt-obliquity.html" class=blk-series__item-link> Earth's Axis Is Tilted </a></li><li class="blk-series__item "><a href="/calendar/aboutseasons.html" class=blk-series__item-link> When Do Seasons Start and End? </a></li><li class="blk-series__item "><a href="/astronomy/solar-analemma.html" class=blk-series__item-link> What Is a Solar Analemma? </a></li></ol></div></div><div class="clip-block clip-block--picker"><h3 class=clip-block__title><a href="/calendar/seasons.html">Astronomical Season Calculator</a></h3><form name=sb_sc method=get action="/calendar/seasons.html" class=picker-city><input class=picker-city__input placeholder="Search for city or place..." autocomplete=off onfocus="ifc(this,'ci',1,14)" name=query id=wcquery type=text><button type=submit class=picker-city__button title=Search><i class="i-font i-search"></i></button></form></div><div class="clip-block clip-block--list"><div class=blk-series><h3 class="blk-series__title clip-block__title">Seasons</h3><ol class=blk-series__list><li class="blk-series__item "><a href="/calendar/spring-equinox.html" class=blk-series__item-link> When Does Spring Start? </a></li><li class="blk-series__item "><a href="/calendar/summer-solstice.html" class=blk-series__item-link> When Does Summer Start? </a></li><li class="blk-series__item "><a href="/calendar/autumnal-equinox.html" class=blk-series__item-link> When Does Fall Start? </a></li><li class="blk-series__item "><a href="/calendar/winter-solstice.html" class=blk-series__item-link> When Does Winter Start? </a></li></ol></div></div><div class="clip-block clip-block--list"><div class=blk-series><h3 class="blk-series__title clip-block__title">Equinoxes & Solstices</h3><ol class=blk-series__list><li class="blk-series__item "><a href="/astronomy/equinox-solstice.html" class=blk-series__item-link> What Are Equinoxes and Solstices? </a></li><li class="blk-series__item "><a href="/calendar/march-equinox.html" class=blk-series__item-link> March Equinox </a></li><li class="blk-series__item "><a href="/calendar/june-solstice.html" class=blk-series__item-link> June Solstice </a></li><li class="blk-series__item "><a href="/calendar/september-equinox.html" class=blk-series__item-link> September Equinox </a></li><li class="blk-series__item "><a href="/calendar/december-solstice.html" class=blk-series__item-link> December Solstice </a></li><li class="blk-series__item "><a href="/astronomy/equinox-not-equal.html" class=blk-series__item-link> Equinox: Day & Night Not Equal </a></li><li class="blk-series__item "><a href="/astronomy/equilux.html" class=blk-series__item-link> Equilux: When Day & Night Are (Actually) Equal </a></li></ol></div></div></aside><aside class="layout-grid__sky layout-grid__sky--sticky article__sky"><fieldset id=ad1><legend>Advertising</legend><div id='div-gpt-com-300x600'><script> AdMgr.dispSlot(0); </script> </div></fieldset></aside></main><aside id=rel-posts class=rel-posts><div class="pdflexi fixed"><h2 class=rel-posts__title>Elsewhere on timeanddate.com</h2><div class=layout-cards> <article class=card> <a href="/news/astronomy/planet-parade-2025" class="card__link" aria-label="Planet Parade 2025: Can We See All the Planets?"> <div class="card__img-wrap"> <img src="https://c.tadst.com/gfx/300x168/orbital-sunrise.jpg?1" width=300 height=168 alt="Planet Parade 2025: Can We See All the Planets?" class=card__img loading=lazy> </div> <section class=card__content> <h4 class=card__title> Planet Parade 2025: Can We See All the Planets? 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