<p>I <strong>despise</strong> leap years. It is a long held grudge I have against them since the first years of my labor life. Every four years, I noticed that I worked a whole day <strong>for free</strong>. Yes, I know that I am conveniently dodging that at absolutely all the years, February is the month where I worked <strong>less than 30 days</strong>, but that wasn't my fault!</p>
https://cdn.pixabay.com/photo/2013/07/13/11/45/seasons-158601_960_720.png
<p>Now, the logic question is: <strong>Why is this day added? Why every four years people have to work one day for free?</strong> (note the populist/socialist tone I'm giving to this).</p>
<p>Well, it turns out that <strong>the way that we divide <a href="https://steemit.com/science/@renzoarg/time-what-is-it-a-multidisciplinary-point-of-view" target="_blank">time</a></strong>, this is, how we separate and count days, months and years, <strong>is related with Earth's orbital movement around the Sun</strong>. And it turns out that neither the way or numbers in that are "round". When I talk about <em>round</em>, I'm not referring to the "0", but obviously to numbers without decimals.</p>

<p>The calendar we use today is practically the same one from Caesar's times, it divides the year in <strong>12 months, for a total of 365 days</strong>. So far, so good, but nature is a bit more complex than perfect numbers and <strong>the actual time that the Earth takes to go around the sun is closer to 365.25 days</strong>. So, we've a leftover of around hours every year. <strong>That is why we add a day every four years, and "<em>problem solved</em>"</strong>.</p>

<p>That's it? This is the end of the article? Of course not! Lets add a couple more questions!</p>

<h3>1/4th of a day per year?!</h3>

<p>To explain this, we need to review our concept of "year". <em>A year is the time Earth takes to go around the sun</em>. Yeah, great, but... <strong>How do I know it did go around?, Where do I place the protractor ruler at to measure those 360°?</strong> <br />
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https://www.mathsisfun.com/geometry/images/protractor.gif
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Astronomers are anything but simple minded, they've different definitions of "year" that vary depending of the <strong>reference point</strong>:</p>

<p><strong>Sidereal year:</strong> Is the time that passes in between two consecutive passes of the Earth over the same point of the orbit, using the stars as reference (for "stars", understand, "others but the Sun"). After one Sidereal year we will see the exact same stars in the exact same position. The problem with this year is that its length is <strong>one day shorter than the year we usually use</strong>.</p>

<p><strong>Solar Year:</strong> Is defined as the time in between the passing of the Sun over the <em>middle equinox</em>. The reference point for this is the vernal (spring) equinox. This year last 365.25 days and is the template for our calendar. The mayor issue with this one is that the vernal equinox day displaces year by year, making a round trip every 26000 years.</p>

<p><strong>Calendar year:</strong> We all know this one, it is based on the solar year. Yet, some communities like the Islamic one, base their calendar in the Moon cycles.</p>
https://cdn.pixabay.com/photo/2016/10/18/17/12/book-1750740_960_720.jpg
<h3>Too many "calendars", and little definition.</h3>

<p>Okey, okey. <strong>The calendar </strong>is a structure of accounting rules for day that <strong>arranges the year measuring time as it passes by</strong>. It is also the same thing that is below that naked woman poster at some car shops. Essentially, calendars are the reflection of social organization; that is why the way we arrange the year was originally linked to seasonal matters, harvesting cycles, animal breeding and river floods, and so on...</p>

<p>Since ancient times, different cultures found a relation between these natural measurable cycles (in Earth and in the sky). <strong>The careful observation of the sky set a course for social organization all around the world</strong>.</p>

<p>We do have, basically, two kinds of calendars: <strong>the solar calendar</strong>, (read above, solar year); and the <strong>lunar calendar</strong>, that bases in the cycle of the moon. <strong>The lunar calendars measure years by "moon months"</strong>, like the Muslim calendar or the Incaic. A lunar month equals to the time that the moon takes in completing a cycle, for example from full moon to full moon.</p>

<p><strong>The calendar of choice is a purely arbitrary option</strong>. Each culture chose one according to the relevance either the Sun or the Moon had in their <strong>vision of the Universe</strong>, their mythology, religion. Some, even mixed them! Like we do, that use the sun to count the year, while we use the moon cycles to measure the month (if you like rounding up a month in 28 days).</p>
<p>A nice case is the Egyptian one, that even shows us the origin of leap years(because <strong>someone</strong> has to be credited of having the idea first, right?). The <strong>Egyptian calendar</strong>, that had a major influence in the calendar we use today and was used back in Julius Caesar's times. The cornerstone of our calendar.</p>

<p>This bunch of people that loved building everlasting rock monuments and drew with no notion of depth, <strong>divided the year in 3, based on agricultural seasons</strong>: Floods (by the end of the summer and autumn), sowing (winter and beginning of spring), harvesting (end of spring and beginning of summer). Even when they based their calendar in the solar cycle, <strong>the beginning of their calendar was highlighted by the yearly flood of the Nile</strong>, that matched the heliacal rising of the Sothis Star (the one we renamed Sirius, we think).</p>
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<p><strong>The heliacal rising of a star is defined by the first appearance of it after a time it was not visible</strong> (not that it "vanished", it was under the horizon. Silly you!); it lasts, more or less, six months. Sothis' matched the same day in the Egyptian calendar every 1460 years. So, <strong>observing, measuring and writing down how Sothis' heliacal rising varied. They found a year of difference every 1460 years; a difference between their calendar and the cycle</strong>. 365 days every 1460 years or, if you want it that way, <strong>one day every 4 years</strong>. A minor adjustment was needed to prevent any discomfort among the priests and prevent Venus' appearance in the sky matching the day Sothis' was supposed to show up (you know, priests and sciences very rarely get along), they decided to add that day every four years and "reset" the difference.</p>

<p>This was taken by Caesar (I like to believe that this was in an after-sex chat in bed; smoking a cigarette and drinking some wine... Cleopatra having pity of Rome's Ignorance told him) and from there, after an unaccountable amount of corrections it landed in February 29th in the <strong>Gregorian Calendar</strong> (the corrections I mention are like, a day every 4 years, exceptions in the multiples of 100 and 400... A topic for a whole new article).</p>

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<p>If you liked this post and its informal way of talking about sciences, please, follow me for more!</p>
<p>Leave a comment either for good or for bad reviews. I take everything as constructive, and I really appreciate the feedback, even from trolls (at least a troll read it before being himself!).</p>
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<h3>Copyrights:</h3>
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<p>All the previously used images are of my authory or under a CC0 license (Source: pixabay), unless openly stated.</p>
<p>All the Images created by me possess a WTFPL licencing and they are free to redistribute, share, copy, paste, modify, sell, crop, paste, clone in whatever way you want.</p>
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