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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::</span>system_clock</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></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-chrono.html">&lt;chrono&gt;</a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">class</span> system_clock<span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<p>&#31867; <code>std::chrono::system_clock</code> &#34920;&#31034;&#31995;&#32479;&#33539;&#22260;&#30340;&#23454;&#26102;&#22721;&#38047;&#12290;</p>
<p>&#23427;&#21487;&#20197;&#19981;&#21333;&#35843;&#65306;&#22823;&#22810;&#25968;&#31995;&#32479;&#19978;&#65292;&#31995;&#32479;&#26102;&#38388;&#21487;&#20197;&#22312;&#20219;&#20309;&#26102;&#20505;&#34987;&#35843;&#33410;&#12290;&#23427;&#26159;&#21807;&#19968;&#26377;&#33021;&#21147;&#26144;&#23556;&#20854;&#26102;&#38388;&#28857;&#21040; C &#39118;&#26684;&#26102;&#38388;&#30340; C++ &#26102;&#38047;&#12290;</p>
<p><code>std::chrono::system_clock</code> &#28385;&#36275;<a href="cpp-named_req-TrivialClock.html"><span style="font-style:italic">&#24179;&#20961;&#26102;&#38047;</span> <span style="font-family: Georgia, &#39;DejaVu Serif&#39;, serif; font-style:italic">(TrivialClock)</span></a> &#30340;&#35201;&#27714;&#12290;</p>
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<p>&#19981;&#25351;&#23450; <code>system_clock</code> &#30340;&#32426;&#20803;&#65292;&#20294;&#22810;&#25968;&#23454;&#29616;&#20351;&#29992; Unix &#26102;&#38388;&#65288;&#21363;&#20174;&#21327;&#35843;&#19990;&#30028;&#26102; (UTC) 1970 &#24180; 1 &#26376; 1 &#26085;&#26143;&#26399;&#22235; 00:00:00 &#24320;&#22987;&#30340;&#26102;&#38388;&#65292;&#19981;&#35745;&#38384;&#31186;&#65289;&#12290;</p>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
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<p><code>system_clock</code> &#24230;&#37327; Unix &#26102;&#38388;&#65288;&#21363;&#20174;&#21327;&#35843;&#19990;&#30028;&#26102; (UTC) 1970 &#24180; 1 &#26376; 1 &#26085;&#26143;&#26399;&#22235; 00:00:00 &#24320;&#22987;&#30340;&#26102;&#38388;&#65292;&#19981;&#35745;&#38384;&#31186;&#65289;&#12290;</p>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<h3><span class="mw-headline" id=".E6.97.B6.E9.97.B4.E7.82.B9.E6.97.8F">&#26102;&#38388;&#28857;&#26063;</span></h3>
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<div>&#23450;&#20041;&#20110;&#21629;&#21517;&#31354;&#38388; <code>std::chrono</code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> Duration<span class="sy1">&gt;</span><br />
<span class="kw1">using</span> sys_time <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>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span>, Duration<span class="sy1">&gt;</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">using</span> sys_seconds <span class="sy1">=</span> sys_time<span class="sy1">&lt;</span><a href="cpp-chrono-duration.html"><span class="kw997">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">seconds</span></span></a><span class="sy1">&gt;</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">using</span> sys_days <span class="sy1">=</span> sys_time<span class="sy1">&lt;</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">days</span><span class="sy1">&gt;</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<div><a href="cpp-chrono-system_clock-operator_ltlt.html"><span class="t-lines"><span>operator&lt;&lt;<span class="t-dsc-small">(std::chrono::sys_time)</span></span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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<td>&#36827;&#34892; sys_time &#19978;&#30340;&#27969;&#36755;&#20986;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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<div><a href="cpp-chrono-system_clock-from_stream.html"><span class="t-lines"><span>from_stream<span class="t-dsc-small">(std::chrono::sys_time)</span></span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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<td>&#25353;&#29031;&#32473;&#23450;&#30340;&#26684;&#24335;&#20174;&#27969;&#20998;&#26512; sys_time<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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<div><a href="cpp-chrono-system_clock-formatter.html"><span class="t-lines"><span>std::formatter<span class="t-dsc-small">&lt;std::chrono::sys_time&gt;</span></span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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<td><span class="t-lc">std::formatter</span> &#30340;&#29305;&#21270;&#65292;&#25353;&#29031;&#25552;&#20379;&#30340;&#26684;&#24335;&#26684;&#24335;&#21270; <code>sys_time</code><br />
<span class="t-mark">(&#31867;&#27169;&#26495;&#29305;&#21270;)</span></td>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">&#25104;&#21592;&#31867;&#22411;</span></h3>
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<td>&#25104;&#21592;&#31867;&#22411;</td>
<td>&#23450;&#20041;</td>
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<td><code>rep</code></td>
<td>&#34920;&#31034;&#26102;&#38047;&#26102;&#38271;&#20013;&#35745;&#27425;&#25968;&#30340;&#26377;&#31526;&#21495;&#31639;&#26415;&#31867;&#22411;</td>
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<td><code>period</code></td>
<td>&#34920;&#31034;&#26102;&#38047;&#35745;&#27425;&#21608;&#26399;&#30340; <span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::ratio</a></span> &#31867;&#22411;&#65292;&#21333;&#20301;&#20026;&#31186;</td>
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<td><code>duration</code></td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1">&lt;</span>rep, period<span class="sy1">&gt;</span></span></span> &#65292;&#36275;&#20197;&#34920;&#31034;&#36127;&#26102;&#38271;</td>
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<td><code>time_point</code></td>
<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><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>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span><span class="sy1">&gt;</span></span></span></td>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.B8.B8.E9.87.8F">&#25104;&#21592;&#24120;&#37327;</span></h3>
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<div><span class="t-lines"><span><span class="t-dsc-small">constexpr bool</span> is_steady</span></span></div>
<div><span class="t-lines"><span><span class="t-cmark">[&#38745;&#24577;]</span></span></span></div>
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<td>&#33509;&#26102;&#38388;&#38388;&#38548;&#35745;&#27425;&#22987;&#32456;&#20026;&#24120;&#25968;&#65292;&#21363;&#32437;&#20351;&#22312;&#35843;&#25972;&#20102;&#22806;&#37096;&#26102;&#38047;&#30340;&#24773;&#20917;&#19979;&#65292;&#35843;&#29992; <a href="cpp-chrono-system_clock-now.html"><tt>now()</tt></a> &#30340;&#36820;&#22238;&#20540;&#20134;&#21333;&#35843;&#36882;&#22686;&#65292;&#21017;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> &#65307;&#21542;&#21017;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span><br />
<span class="t-mark">(&#20844;&#24320;&#38745;&#24577;&#25104;&#21592;&#24120;&#37327;)</span></td>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">&#25104;&#21592;&#20989;&#25968;</span></h3>
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<div><a href="cpp-chrono-system_clock-now.html"><span class="t-lines"><span>now</span></span></a></div>
<div><span class="t-lines"><span><span class="t-cmark">[&#38745;&#24577;]</span></span></span></div>
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<td>&#36820;&#22238;&#34920;&#31034;&#26102;&#38388;&#20013;&#24403;&#21069;&#28857;&#30340; <span class="t-lc"><a href="cpp-chrono-time_point.html">std::chrono::time_point</a></span><br />
<span class="t-mark">(&#20844;&#24320;&#38745;&#24577;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div><a href="cpp-chrono-system_clock-to_time_t.html"><span class="t-lines"><span>to_time_t</span></span></a></div>
<div><span class="t-lines"><span><span class="t-cmark">[&#38745;&#24577;]</span></span></span></div>
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<td>&#36716;&#25442;&#31995;&#32479;&#26102;&#38047;&#26102;&#38388;&#28857;&#20026; <span class="t-lc"><a href="cpp-chrono-c-time_t.html">std::time_t</a></span><br />
<span class="t-mark">(&#20844;&#24320;&#38745;&#24577;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-chrono-system_clock-from_time_t.html"><span class="t-lines"><span>from_time_t</span></span></a></div>
<div><span class="t-lines"><span><span class="t-cmark">[&#38745;&#24577;]</span></span></span></div>
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<td>&#36716;&#25442; <span class="t-lc"><a href="cpp-chrono-c-time_t.html">std::time_t</a></span> &#21040;&#31995;&#32479;&#26102;&#38047;&#26102;&#38388;&#28857;<br />
<span class="t-mark">(&#20844;&#24320;&#38745;&#24577;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">&#27880;&#35299;</span></h3>
<p><code>system_clock</code> &#30340;&#26102;&#38388;&#20540;&#33021;&#30001;&#25805;&#20316;&#31995;&#32479;&#22312;&#20869;&#37096;&#35843;&#25972;&#21040;&#20219;&#20309;&#26102;&#38388;&#65292;&#20363;&#22914;&#30001;&#20110; NTP &#21516;&#27493;&#25110;&#29992;&#25143;&#26356;&#25913;&#31995;&#32479;&#30340;&#26102;&#38047;&#12290;&#28982;&#32780;&#22799;&#20196;&#26102;&#21644;&#26102;&#21306;&#26356;&#25913;&#19981;&#24433;&#21709;&#23427;&#65292;&#22240;&#20026;&#23427;&#22522;&#20110; <a rel="nofollow" class="external text" href="https://en.wikipedia.org/wiki/Coordinated_Universal_Time">UTC</a> &#26102;&#21306;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div><a href="cpp-chrono-steady_clock.html"><span class="t-lines"><span>steady_clock</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>&#20915;&#19981;&#20250;&#35843;&#25972;&#30340;&#21333;&#35843;&#26102;&#38047;<br />
<span class="t-mark">(&#31867;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-chrono-high_resolution_clock.html"><span class="t-lines"><span>high_resolution_clock</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>&#25317;&#26377;&#21487;&#29992;&#30340;&#26368;&#30701;&#22016;&#21970;&#21608;&#26399;&#30340;&#26102;&#38047;<br />
<span class="t-mark">(&#31867;)</span></td>
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