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gobyexample/public/time-formatting-parsing
Mark McGranaghan 915697101b More consistent use of layout vs format
2014-04-15 18:14:23 -07:00

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<title>Go by Example: Time Formatting / Parsing</title>
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<div class="example" id="time-formatting-parsing">
<h2><a href="./">Go by Example</a>: Time Formatting / Parsing</h2>
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<p>Go supports time formatting and parsing via
pattern-based layouts.</p>
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<a href="http://play.golang.org/p/SGS6wIVnDd"><img title="Run code" src="play.png" class="run" /></a>
<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
</pre></div>
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<div class="highlight"><pre><span class="kn">import</span> <span class="s">&quot;fmt&quot;</span>
<span class="kn">import</span> <span class="s">&quot;time&quot;</span>
</pre></div>
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
<span class="nx">p</span> <span class="o">:=</span> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span>
</pre></div>
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<p>Here&rsquo;s a basic example of formatting a time
according to RFC3339, using the corresponding layout
constant.</p>
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<div class="highlight"><pre> <span class="nx">t</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Now</span><span class="p">()</span>
<span class="nx">p</span><span class="p">(</span><span class="nx">t</span><span class="p">.</span><span class="nx">Format</span><span class="p">(</span><span class="nx">time</span><span class="p">.</span><span class="nx">RFC3339</span><span class="p">))</span>
</pre></div>
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<p>Time parsing uses the same layout values as <code>Format</code>.</p>
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<div class="highlight"><pre> <span class="nx">t1</span><span class="p">,</span> <span class="nx">e</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Parse</span><span class="p">(</span>
<span class="nx">time</span><span class="p">.</span><span class="nx">RFC3339</span><span class="p">,</span>
<span class="s">&quot;2012-11-01T22:08:41+00:00&quot;</span><span class="p">)</span>
<span class="nx">p</span><span class="p">(</span><span class="nx">t1</span><span class="p">)</span>
</pre></div>
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<p><code>Format</code> and <code>Parse</code> uses example-based layouts. Usually
you&rsquo;ll use a constant from <code>time</code> for these layouts, but
you can also supply custom layouts. Layouts must use the
reference time <code>Mon Jan 2 15:04:05 MST 2006</code> to show the
pattern with which to format/parse a given time/string.
The example time must be exactly as shown: the year 2006,
15 for the hour, Monday for the day of the week, etc.</p>
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<div class="highlight"><pre> <span class="nx">p</span><span class="p">(</span><span class="nx">t</span><span class="p">.</span><span class="nx">Format</span><span class="p">(</span><span class="s">&quot;3:04PM&quot;</span><span class="p">))</span>
<span class="nx">p</span><span class="p">(</span><span class="nx">t</span><span class="p">.</span><span class="nx">Format</span><span class="p">(</span><span class="s">&quot;Mon Jan _2 15:04:05 2006&quot;</span><span class="p">))</span>
<span class="nx">p</span><span class="p">(</span><span class="nx">t</span><span class="p">.</span><span class="nx">Format</span><span class="p">(</span><span class="s">&quot;2006-01-02T15:04:05.999999-07:00&quot;</span><span class="p">))</span>
<span class="nx">form</span> <span class="o">:=</span> <span class="s">&quot;3 04 PM&quot;</span>
<span class="nx">t2</span><span class="p">,</span> <span class="nx">e</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Parse</span><span class="p">(</span><span class="nx">form</span><span class="p">,</span> <span class="s">&quot;8 41 PM&quot;</span><span class="p">)</span>
<span class="nx">p</span><span class="p">(</span><span class="nx">t2</span><span class="p">)</span>
</pre></div>
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<p>For purely numeric representations you can also
use standard string formatting with the extracted
components of the time value.</p>
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<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Printf</span><span class="p">(</span><span class="s">&quot;%d-%02d-%02dT%02d:%02d:%02d-00:00\n&quot;</span><span class="p">,</span>
<span class="nx">t</span><span class="p">.</span><span class="nx">Year</span><span class="p">(),</span> <span class="nx">t</span><span class="p">.</span><span class="nx">Month</span><span class="p">(),</span> <span class="nx">t</span><span class="p">.</span><span class="nx">Day</span><span class="p">(),</span>
<span class="nx">t</span><span class="p">.</span><span class="nx">Hour</span><span class="p">(),</span> <span class="nx">t</span><span class="p">.</span><span class="nx">Minute</span><span class="p">(),</span> <span class="nx">t</span><span class="p">.</span><span class="nx">Second</span><span class="p">())</span>
</pre></div>
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<p><code>Parse</code> will return an error on malformed input
explaining the parsing problem.</p>
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<div class="highlight"><pre> <span class="nx">ansic</span> <span class="o">:=</span> <span class="s">&quot;Mon Jan _2 15:04:05 2006&quot;</span>
<span class="nx">_</span><span class="p">,</span> <span class="nx">e</span> <span class="p">=</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Parse</span><span class="p">(</span><span class="nx">ansic</span><span class="p">,</span> <span class="s">&quot;8:41PM&quot;</span><span class="p">)</span>
<span class="nx">p</span><span class="p">(</span><span class="nx">e</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>
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<div class="highlight"><pre><span class="gp">$</span> go run <span class="nb">time</span>-formatting-parsing.go
<span class="go">2014-04-15T18:00:15-07:00</span>
<span class="go">2012-11-01 22:08:41 +0000 +0000</span>
<span class="go">6:00PM</span>
<span class="go">Tue Apr 15 18:00:15 2014</span>
<span class="go">2014-04-15T18:00:15.161182-07:00</span>
<span class="go">0000-01-01 20:41:00 +0000 UTC</span>
<span class="go">2014-04-15T18:00:15-00:00</span>
<span class="go">parsing time &quot;8:41PM&quot; as &quot;Mon Jan _2 15:04:05 2006&quot;: \</span>
<span class="go"> cannot parse &quot;8:41PM&quot; as &quot;Mon&quot;</span>
</pre></div>
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<p class="next">
Next example: <a href="random-numbers">Random Numbers</a>.
</p>
<p class="footer">
by <a href="https://twitter.com/mmcgrana">@mmcgrana</a> | <a href="mailto:mmcgrana@gmail.com">feedback</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/time-formatting-parsing">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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