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</div> <div class=site-nav-bar__blur id=site-nav-blur></div> </div> </nav> </div> </div><div id=po1 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="/calendar/" class=fx>Calendar</a>   <a target=_top href="/calendar/days/" class=fx>Days of the week</a>   Why 7 Days per Week?</div></div></div></div><main class="article layout-grid layout-grid--article"><article class="layout-grid__main article__content"><h1 class=article__title>Why Does a Week Have 7 Days?</h1><h4 class=article__sub-title></h4><p class=article__byline>By <a href='/company/team-editorial#kb'>Konstantin Bikos</a></p><p class=article__lead>It's Monday and you are looking forward to the weekend. Why do you have to wait 5 days until Saturday? And how come the day after Monday is Tuesday and not, say, Sunday? You have an ancient people in modern-day Iraq to thank.</p><div class=article__body><figure class="article__figure "><div class=article__img-container><img src="//c.tadst.com/gfx/600x337/statue-lion-babylon-iraq.jpg?1" width=600 height=337 title="The statue of the lion of Babylon was discovered in 1876. It is considered among the most important symbols of Babylon." alt="3 men next to the black basalt statue of the lion of Babylon which depicts a lion standing above a laying human in today's Iraq. March 20, 2015." class=article__img srcset="//c.tadst.com/gfx/900x506/statue-lion-babylon-iraq.jpg?1 1.5x,//c.tadst.com/gfx/1200x675/statue-lion-babylon-iraq.jpg?1 2x"></div><figcaption><p class=article__img-caption>The lion of Babylon statue in Iraq.</p><p class=article__img-credit>©iStockphoto.com/rasoulali</p></figcaption></figure><h2>A Week for Each Moon Phase</h2><p>The reason why we organize our lives around a <a href="/calendar/days/">7-day week</a> is, quite literally, above our heads. Like <a href="/date/perfect-calendar.html">many other calendars</a>, today's <a href="/calendar/gregorian-calendar.html">Gregorian calendar</a> is ultimately based on the phases of the Moon. It takes the Moon <a href="/astronomy/moon/lunar-month.html" title="What is a lunar month?">around 29.5 days</a> to cycle through all <a href="/astronomy/moon/phases.html">Moon phases</a>.</p><p class=large-link><a href="/moon/phases/">Moon phases in your city</a></p><p>For everyday purposes, this is a fairly long and impractical time span, so it makes sense to break it down into smaller segments.</p><p>Enter the Babylonians. This ancient society, who lived in Mesopotamia in what is now <a href="/worldclock/iraq">Iraq</a>, rounded the Moon cycle down to 28 days and divided this time span into 4 periods of 7 days each, using leap days to stay in sync with the Moon phases in the long run.</p><p>This 7-day structure is also believed to have ultimately informed a number of popular creation myths, such as the Book of Genesis in the Hebrew and Christian Bibles, which states that God created the world in seven days: six days of work followed by one day of rest.</p><p class=large-link><a href="/date/leapyear.html">Leap days in our modern calendar</a></p><h2>7 Planets, 7 Days</h2><p>Avid astronomers and astrologers, the Babylonians developed a kind of horoscope around 500 <a href="/calendar/ce-bce-what-do-they-mean.html">BCE</a> where each day of the week was assigned to one of the <em>classical planets</em> – the seven non-fixed celestial bodies visible to the naked eye. These are <a href="/astronomy/sun/about">the Sun</a>, <a href="/astronomy/moon/about.html">the Moon</a>, <a href="/astronomy/planets/mars/">Mars</a>, <a href="/astronomy/planets/mercury/">Mercury</a>, <a href="/astronomy/planets/jupiter/">Jupiter</a>, <a href="/astronomy/planets/venus/">Venus</a>, and <a href="/astronomy/planets/saturn/">Saturn</a>.</p><p>Some historical sources claim that the connection between the days of the week and the classical planets was introduced later by the ancient Greeks.</p><p class=large-link><a href="/astronomy/night/">Find the planets in the night sky</a></p><p class=large-link><a href="/astronomy/planets/planet">What is a planet?</a></p><h2>Roman Gods Named Days of the Week</h2><p>However, historians generally agree that it was the <a href="/calendar/roman-calendar.html">Romans</a> who, a few hundred years later, added many features of the modern 7-day week by adapting the Babylonian system to their world view.</p><p>From around the 1st century BCE, they introduced a system where each day was named after one of their pagan gods, each of whom was associated with one of the classical planets. For example, Saturday was <em>dies Saturni</em>, the day of Saturn.</p><p>In most Latin-based languages, the names of the weekdays still reveal this connection to the classical planets. However, in many cases, the Roman deities have been replaced by their Norse or Germanic equivalents.</p><div class="detail info"><h3>Read More About Each Day of the Week</h3><p><a href="/calendar/days/monday.html"><strong>Monday</strong></a> | <a href="/calendar/days/tuesday.html"><strong>Tuesday</strong></a> | <a href="/calendar/days/wednesday.html"><strong>Wednesday</strong></a> | <a href="/calendar/days/thursday.html"><strong>Thursday</strong></a> | <a href="/calendar/days/friday.html"><strong>Friday</strong></a> | <a href="/calendar/days/saturday.html"><strong>Saturday</strong></a> | <a href="/calendar/days/sunday.html"><strong>Sunday</strong></a></p></div><h2 id=the>The Order of the Weekdays</h2><p>Like the modern names of the weekdays, their order within a week has its roots in ancient Rome. The Romans observed the speed at which the classical planets crossed the sky and concluded that the fastest object must have the shortest distance to the Earth, while the slowest object was believed to be farthest away.</p><p class=large-link><a href="/astronomy/planets/distance">What is the actual distance to the planets?</a></p><p class=large-link><a href="/astronomy/moon/distance.html">How far is the Moon from Earth?</a></p><p>This resulted in the following order, from greatest to shortest assumed distance from Earth, displayed here with the associated day of the week:</p><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/weekday-planets.png?1" width=600 height=337 alt="Illustration image" class=article__img srcset="//c.tadst.com/gfx/900x506/weekday-planets.png?1 1.5x,//c.tadst.com/gfx/1200x675/weekday-planets.png?1 2x"></div><div class=article__lightbox><img src="//c.tadst.com/gfx/1200x675/weekday-planets.png?1" width=1200 height=675 alt="Illustration image" class=article__img-large loading=lazy></div><figcaption><p class=article__img-caption>The classical planets and their perceived distance from Earth, with associated days of the week.</p></figcaption></figure><ul><li>Saturn (Saturday)</li><li>Jupiter (Thursday)</li><li>Mars (Tuesday)</li><li>Sun (Sunday)</li><li>Venus (Friday)</li><li>Mercury (Wednesday)</li><li>Moon (Monday)</li></ul><p class=large-link><a href="/calendar/days/first-day-of-the-week.html">What is the first day of the week?</a></p><h2>Planetary Hours</h2><p>The ancient Romans also believed that each hour of the day was governed by one of the deities associated with the celestial bodies. According to this <em>planetary hours</em> system, the 1st hour of the 1st day of the week was thought to be governed by the Moon. Following the above order for each consecutive hour, the 2nd hour was steered by Saturn, the 3rd hour by Jupiter, and so on.</p><p>By applying this pattern to all 168 hours of the week (see image), the Romans associated the <em>1st hour</em> of each weekday with following celestial bodies:</p><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/weekday-planets-order.png?1" width=600 height=337 alt="Illustration image" class=article__img srcset="//c.tadst.com/gfx/900x506/weekday-planets-order.png?1 1.5x,//c.tadst.com/gfx/1200x675/weekday-planets-order.png?1 2x"></div><div class=article__lightbox><img src="//c.tadst.com/gfx/1200x675/weekday-planets-order.png?1" width=1200 height=675 alt="Illustration image" class=article__img-large loading=lazy></div><figcaption><p class=article__img-caption>Roman planetary hours.</p></figcaption></figure><ul><li>Day 1: Moon (Monday)</li><li>Day 2: Mars (Tuesday)</li><li>Day 3: Mercury (Wednesday)</li><li>Day 4: Jupiter (Thursday)</li><li>Day 5: Venus (Friday)</li><li>Day 6: Saturn (Saturday)</li><li>Day 7: Sun (Sunday)</li></ul><p>This corresponds to the order of today's 7-day week.</p><p class=large-link><a href="/date/birthday.html">Planet years: how old are you on Mars or Venus?</a></p><p class=article__htags><strong>Topics: </strong><a href="/topics/weekdays">Weekdays</a>, <a href="/topics/dates">Dates</a></p></div></article><aside class="layout-grid__sidebar article__sidebar"><div class="clip-block clip-block--calendar"><h3 class=clip-block__title>Create Calendar With Holidays</h3><form name=cf id=cf class="small ten" method=get action="/scripts/createcal2.php"><div class=form-row><label class="inline six"><input type=radio name=typ value=0 checked>Full year</label><input placeholder=yyyy type=text autocomplete=off tad-va=date onfocus="window.ifc&&ifc(this,'y')" pattern="[0-9]*" maxlength=4 size=9 id=boxyear name=year title="Enter year as a 4-digit number." class=six value=2025></div><div class=form-row><label class="inline six"><input type=radio name=typ value=1>Month</label><select id=month name=month class="inline six" onchange='document.cf.typ[1].checked=true'><option value=1>January</option><option value=2 selected>February</option><option value=3>March</option><option value=4>April</option><option value=5>May</option><option value=6>June</option><option value=7>July</option><option value=8>August</option><option value=9>September</option><option value=10>October</option><option value=11>November</option><option value=12>December</option></select></div><div class=form-row><select id=country name=country class="inline twelve" title="Select country"><option value=29>Australia</option><option value=27>Canada</option><option value=35>India</option><option value=32>Ireland</option><option value=30>New Zealand</option><option value=9>United Kingdom</option><option value=1>United States</option><option value=160>Afghanistan</option><option value=93>Albania</option><option value=123>Algeria</option><option value=207>American Samoa</option><option value=97>Andorra</option><option value=127>Angola</option><option value=217>Anguilla</option><option value=221>Antigua and Barbuda</option><option value=37>Argentina</option><option value=102>Armenia</option><option value=177>Aruba</option><option value=29>Australia</option><option value=36>Austria</option><option value=85>Azerbaijan</option><option value=110>Bahamas</option><option value=133>Bahrain</option><option value=233>Bangladesh</option><option value=112>Barbados</option><option value=83>Belarus</option><option value=31>Belgium</option><option value=193>Belize</option><option value=148>Benin</option><option value=113>Bermuda</option><option value=198>Bhutan</option><option value=53>Bolivia</option><option value=86>Bosnia and Herzegovina</option><option value=144>Botswana</option><option value=33>Brazil</option><option value=224>British Virgin Islands</option><option value=79>Brunei</option><option value=73>Bulgaria</option><option value=165>Burkina Faso</option><option value=166>Burundi</option><option value=140>Cambodia</option><option value=134>Cameroon</option><option value=27>Canada</option><option value=157>Cape Verde</option><option value=111>Cayman Islands</option><option value=167>Central African Republic</option><option value=161>Chad</option><option value=43>Chile</option><option value=41>China</option><option value=46>Colombia</option><option value=172>Comoros</option><option value=84>Congo DR</option><option value=208>Cook Islands</option><option value=58>Costa Rica</option><option value=28>Croatia</option><option value=51>Cuba</option><option value=189>Curaçao</option><option value=94>Cyprus</option><option value=3>Czechia</option><option value=2>Denmark</option><option value=153>Djibouti</option><option value=229>Dominica</option><option value=52>Dominican Republic</option><option value=49>Ecuador</option><option value=80>Egypt</option><option value=55>El Salvador</option><option value=61>Equatorial Guinea</option><option value=168>Eritrea</option><option value=72>Estonia</option><option value=81>Ethiopia</option><option value=219>Falkland Islands</option><option value=175>Faroe Islands</option><option value=180>Fiji</option><option value=24>Finland</option><option value=5>France</option><option value=235>French Guiana</option><option value=205>French Polynesia</option><option value=150>Gabon</option><option value=149>Gambia</option><option value=87>Georgia</option><option value=8>Germany</option><option value=118>Ghana</option><option value=119>Gibraltar</option><option value=11>Greece</option><option value=138>Greenland</option><option value=22>Gregorian calendar</option><option value=182>Grenada</option><option value=236>Guadeloupe</option><option value=188>Guam</option><option value=50>Guatemala</option><option value=191>Guernsey</option><option value=169>Guinea</option><option value=173>Guinea-Bissau</option><option value=227>Guyana</option><option value=103>Haiti</option><option value=54>Honduras</option><option value=42>Hong Kong</option><option value=12>Hungary</option><option value=88>Iceland</option><option value=35>India</option><option value=65>Indonesia</option><option value=75>Iran</option><option value=109>Iraq</option><option value=32>Ireland</option><option value=234>Isle of Man</option><option value=34>Israel</option><option value=13>Italy</option><option value=125>Ivory Coast</option><option value=117>Jamaica</option><option value=26>Japan</option><option value=192>Jersey</option><option value=44>Jordan</option><option value=23>Julian calendar</option><option value=82>Kazakhstan</option><option value=105>Kenya</option><option value=194>Kiribati</option><option value=120>Kosovo</option><option value=108>Kuwait</option><option value=136>Kyrgyzstan</option><option value=176>La Réunion</option><option value=200>Laos</option><option value=89>Latvia</option><option value=121>Lebanon</option><option value=163>Lesotho</option><option value=129>Liberia</option><option value=124>Libya</option><option value=96>Liechtenstein</option><option value=90>Lithuania</option><option value=17>Luxembourg</option><option value=186>Macau</option><option value=156>Madagascar</option><option value=162>Malawi</option><option value=69>Malaysia</option><option value=201>Maldives</option><option value=152>Mali</option><option value=95>Malta</option><option value=213>Marshall Islands</option><option value=181>Martinique</option><option value=210>Mauritania</option><option value=143>Mauritius</option><option value=171>Mayotte</option><option value=40>Mexico</option><option value=211>Micronesia</option><option value=91>Moldova</option><option value=99>Monaco</option><option value=185>Mongolia</option><option value=101>Montenegro</option><option value=220>Montserrat</option><option value=106>Morocco</option><option value=126>Mozambique</option><option value=190>Myanmar</option><option value=130>Namibia</option><option value=215>Nauru</option><option value=187>Nepal</option><option value=204>New Caledonia</option><option value=30>New Zealand</option><option value=57>Nicaragua</option><option value=158>Niger</option><option value=77>Nigeria</option><option value=237>Norfolk Island</option><option value=183>North Korea</option><option value=92>North Macedonia</option><option value=225>Northern Mariana Islands</option><option value=18>Norway</option><option value=135>Oman</option><option value=64>Pakistan</option><option value=212>Palau</option><option value=60>Panama</option><option value=202>Papua New Guinea</option><option value=56>Paraguay</option><option value=47>Peru</option><option value=67>Philippines</option><option value=14>Poland</option><option value=15>Portugal</option><option value=114>Puerto Rico</option><option value=107>Qatar</option><option value=151>Republic of the Congo</option><option value=19>Romania</option><option value=20>Russia</option><option value=128>Rwanda</option><option value=232>Saint Barthélemy</option><option value=170>Saint Helena</option><option value=226>Saint Kitts and Nevis</option><option value=218>Saint Lucia</option><option value=231>Saint Martin</option><option value=228>Saint Pierre and Miquelon</option><option value=222>Saint Vincent and the Grenadines</option><option value=206>Samoa</option><option value=98>San Marino</option><option value=174>São Tomé and Príncipe</option><option value=74>Saudi Arabia</option><option value=147>Senegal</option><option value=38>Serbia</option><option value=154>Seychelles</option><option value=164>Sierra Leone</option><option value=63 selected>Singapore</option><option value=230>Sint Maarten</option><option value=39>Slovakia</option><option value=45>Slovenia</option><option value=209>Solomon Islands</option><option value=137>Somalia</option><option value=62>South Africa</option><option value=70>South Korea</option><option value=146>South Sudan</option><option value=16>Spain</option><option value=116>Sri Lanka</option><option value=145>Sudan</option><option value=178>Suriname</option><option value=155>Swaziland</option><option value=21>Sweden</option><option value=10>Switzerland</option><option value=132>Syria</option><option value=71>Taiwan</option><option value=197>Tajikistan</option><option value=115>Tanzania</option><option value=68>Thailand</option><option value=25>The Netherlands</option><option value=199>Timor-Leste</option><option value=159>Togo</option><option value=195>Tonga</option><option value=104>Trinidad and Tobago</option><option value=122>Tunisia</option><option value=4>Turkey</option><option value=196>Turkmenistan</option><option value=223>Turks and Caicos Islands</option><option value=214>Tuvalu</option><option value=179>U.S. Virgin Islands</option><option value=139>Uganda</option><option value=76>Ukraine</option><option value=66>United Arab Emirates</option><option value=9>United Kingdom</option><option value=1>United States</option><option value=59>Uruguay</option><option value=184>Uzbekistan</option><option value=203>Vanuatu</option><option value=100>Vatican City</option><option value=48>Venezuela</option><option value=78>Vietnam</option><option value=216>Wallis and Futuna</option><option value=131>Yemen</option><option value=142>Zambia</option><option value=141>Zimbabwe</option></select></div><div class=form-row><input type=submit value="View Calendar"></div></form></div><div class="clip-block clip-block--list"><div class=blk-series><h3 class="blk-series__title clip-block__title">The Days of the Week</h3><ol class=blk-series__list><li class="blk-series__item "><a href="/calendar/days/monday.html" class=blk-series__item-link> Monday </a></li><li class="blk-series__item "><a href="/calendar/days/tuesday.html" class=blk-series__item-link> Tuesday </a></li><li class="blk-series__item "><a href="/calendar/days/wednesday.html" class=blk-series__item-link> Wednesday </a></li><li class="blk-series__item "><a href="/calendar/days/thursday.html" class=blk-series__item-link> Thursday </a></li><li class="blk-series__item "><a href="/calendar/days/friday.html" class=blk-series__item-link> Friday </a></li><li class="blk-series__item "><a href="/calendar/days/saturday.html" class=blk-series__item-link> Saturday </a></li><li class="blk-series__item "><a href="/calendar/days/sunday.html" class=blk-series__item-link> Sunday </a></li><li class="blk-series__item "><a href="/calendar/days/first-day-of-the-week.html" class=blk-series__item-link> What Is the First Day of the Week? </a></li><li class="blk-series__item "><a href="/holidays/why-we-have-weekends.html" class=blk-series__item-link> Why Do We Have Weekends? </a></li><li class="blk-series__item "><a href="/calendar/days/long-weekend.html" class=blk-series__item-link> Long Weekends and Bank Holidays </a></li><li class="blk-series__item "><a href="/date/week-numbers.html" class=blk-series__item-link> What Are Week Numbers? </a></li><li class="blk-series__item active"> Why Does Tuesday Follow Monday? </li></ol><p class=blk-series__footer><a href="/calendar/" class=read-more> Calendar Servies </a></p></div></div><div class="clip-block clip-block--tool"><h3 class=clip-block__title><a href="/calendar/weekdays.html">Find Next Occurrence Of...</a></h3><form method=get action="/scripts/goweekdays.php"><select id=weekd name=weekd class=four><option value=7>Sunday</option><option value=1>Monday</option><option value=2>Tuesday</option><option value=3>Wednesday</option><option value=4>Thursday</option><option value=5 selected>Friday</option><option value=6>Saturday</option></select>   <select id=day name=day class=three><option value=1>1</option><option value=2>2</option><option value=3>3</option><option value=4>4</option><option value=5>5</option><option value=6>6</option><option value=7>7</option><option value=8>8</option><option value=9>9</option><option value=10>10</option><option value=11>11</option><option value=12>12</option><option value=13 selected>13</option><option value=14>14</option><option value=15>15</option><option value=16>16</option><option value=17>17</option><option value=18>18</option><option value=19>19</option><option value=20>20</option><option value=21>21</option><option value=22>22</option><option value=23>23</option><option value=24>24</option><option value=25>25</option><option value=26>26</option><option value=27>27</option><option value=28>28</option><option value=29>29</option><option value=30>30</option><option value=31>31</option></select>   <input type=submit value=Go class=three></form></div></aside><aside class="layout-grid__sky layout-grid__sky--sticky article__sky"><fieldset 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