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<title>std::chrono::time_point&lt;Clock,Duration&gt;::time_since_epoch</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::time_point&lt;Clock,Duration&gt;::</span>time_since_epoch</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-chrono.html">chrono</a>&lrm; | <a href="cpp-chrono-time_point.html">time point</a></span></div>
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<div><span class="mw-geshi cpp source-cpp">duration time_since_epoch<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span><br />
<span class="t-mark-rev t-until-cxx14">(C++14 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> duration time_since_epoch<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 &#36215;)</span></td>
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<p>&#36820;&#22238;&#34920;&#31034; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#19982; <code>clock</code> &#30340;&#32426;&#20803;&#38388;&#30340;&#26102;&#38388;&#37327;&#30340; <span class="t-lc"><a href="cpp-chrono-duration.html">duration</a></span> &#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<p>&#65288;&#26080;&#65289;</p>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#27492; <code>time_point</code> &#19982; <code>clock</code> &#30340;&#32426;&#20803;&#38388;&#30340;&#26102;&#38388;&#37327;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;chrono&gt;</span>
<span class="co2">#include &lt;ctime&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw4">auto</span> p0 <span class="sy1">=</span> <a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1">&lt;</span><a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a><span class="sy1">&gt;</span><span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">auto</span> p1 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span><span class="sy4">::</span><span class="me2">now</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">auto</span> p2 <span class="sy1">=</span> p1 <span class="sy2">-</span> <a href="cpp-chrono-duration.html"><span class="kw999">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">hours</span></span></a><span class="br0">(</span><span class="nu0">24</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">auto</span> epoch_time <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span><span class="sy4">::</span><span class="me2">to_time_t</span><span class="br0">(</span>p0<span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;epoch: &quot;</span> <span class="sy1">&lt;&lt;</span> <a href="cpp-chrono-c-ctime.html"><span class="kw1016">std::<span class="me2">ctime</span></span></a><span class="br0">(</span><span class="sy3">&amp;</span>epoch_time<span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">auto</span> today_time <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span><span class="sy4">::</span><span class="me2">to_time_t</span><span class="br0">(</span>p1<span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;today: &quot;</span> <span class="sy1">&lt;&lt;</span> <a href="cpp-chrono-c-ctime.html"><span class="kw1016">std::<span class="me2">ctime</span></span></a><span class="br0">(</span><span class="sy3">&amp;</span>today_time<span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;hours since epoch: &quot;</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-chrono-duration-duration_cast.html"><span class="kw1000">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration_cast</span></span></a><span class="sy1">&lt;</span><a href="cpp-chrono-duration.html"><span class="kw999">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">hours</span></span></a><span class="sy1">&gt;</span><span class="br0">(</span>
p1.<span class="me1">time_since_epoch</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;yesterday, hours since epoch: &quot;</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-chrono-duration-duration_cast.html"><span class="kw1000">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration_cast</span></span></a><span class="sy1">&lt;</span><a href="cpp-chrono-duration.html"><span class="kw999">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">hours</span></span></a><span class="sy1">&gt;</span><span class="br0">(</span>
p2.<span class="me1">time_since_epoch</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
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<pre class="de1">epoch: Thu Jan 1 00:00:00 1970
today: Fri Jun 30 10:44:11 2017
hours since epoch: 416338
yesterday, hours since epoch: 416314</pre></div>
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