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<!--replace-end-7--><!--replace-end-4--><!--replace-end-1--></head><body><div class="ui fluid container universe"><!--replace-start-2--><!--replace-start-3--><!--replace-start-6--><div class="ui text container" id="zettel-container" style="position: relative"><div class="zettel-view"><article class="ui raised attached segment zettel-content"><div class="pandoc"><h1 id="title-h1">Time and computers</h1><h2 id="epochs-and-unix-time">Epochs and Unix Time</h2><p>An epoch is a period of time identified by a starting point.</p><p>The standard epoch for measuring against is known colloqially as “Unix Time”: midnight on 1st January 1970. Unix time is the number of seconds that have elapsed since this point. This is the standard for Windows and most unix systems.</p><p>For example midnight on 2nd January 1970 would be 86400 seconds since the epoch. The deduction is as follows:</p><pre><code class="language-none">60 * 60 * 24 = 86400</code></pre><p>We are multiplpying the number of seconds in a minute by the number of minutes in an hour by the number of hours in a day.</p><p>To represent times and dates before 1970, we use negative integers.</p><h2 id="utc-and-time-zones">UTC and time zones</h2><p>“Coordinated Universal Time” (UTC) is the time standard against which the world’s timekeeping is synchronized. It is not itself a timezone, it is a transcendent standard that defines what time zones are.</p><p>Time zones are defined relative to UTC, by their offset to this value.</p><p>For example North America is behind UTC by five or six hours hence uses the notation UTC-5:00 or UTC-6:00.</p><p>UTC is the successor to GMT of which there were variances necessitating a universal value. Despite this GMT is equal to UTC+00:00 so apart from when daylight saving is in effect in the UK, GMT = UTC.</p><p>Depending on your locale, relative to UTC, you will get different outputs when you attempt to log Unix Time.</p><p>Also daylight savings can impact on the outputs. For instance for half of the year, when DST applies, the UK is UTC+01:00.</p><h2 id="examples-in-python">Examples in Python</h2><p>The following gives us the unix seconds in my current time zone (GMT DST):</p><pre><code class="py language-py">import time
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print(time.time())
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# 1714322393.2929392</code></pre><p>If I want UTC, I can do:</p><pre><code class="py language-py">import datetime
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print(datetime.datetime.utcnow().strftime('%s'))
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# '1714318952'</code></pre><p>We see clearly that they are not identical.</p></div></article><nav class="ui attached segment deemphasized bottomPane" id="neuron-tags-pane"><div><span class="ui basic label zettel-tag" title="Tag">time</span><span class="ui basic label zettel-tag" title="Tag">unix</span></div></nav><nav class="ui bottom attached icon compact inverted menu blue" id="neuron-nav-bar"><!--replace-start-9--><!--replace-end-9--><a class="right item" href="impulse.html" title="Open Impulse"><i class="wave square icon"></i></a></nav></div></div><!--replace-end-6--><!--replace-end-3--><!--replace-end-2--><div class="ui center aligned container footer-version"><div class="ui tiny image"><a href="https://neuron.zettel.page"><img alt="logo" src="https://raw.githubusercontent.com/srid/neuron/master/assets/neuron.svg" title="Generated by Neuron 1.9.35.3" /></a></div></div></div></body></html> |