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<div class="identifier-type">function</div><div class="header"><chrono></div><h1 itemprop="name"><span class="namespace" title="namespace std::chrono">std::chrono::</span><span class="class" title="class time_zone">time_zone::</span><span class="token">to_sys</span><span class="cpp cpp20" title="C++20で追加">(C++20)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">template</span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Duration</span><span class="o">></span>
<span class="n"><a href="../sys_time.html">sys_time</a></span><span class="o"><</span><span class="n"><a href="../common_type.html">common_type_t</a></span><span class="o"><</span><span class="n">Duration</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../duration_aliases.html">seconds</a></span><span class="o">>></span>
<span class="w"> </span><span class="n">to_sys</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../local_time.html">local_time</a></span><span class="o"><</span><span class="n">Duration</span><span class="o">>&</span><span class="w"> </span><span class="n">tp</span><span class="p">)</span><span class="w"> </span><span class="k">const</span><span class="p">;</span><span class="w"> </span><span class="c1">// (1) C++20</span>
<span class="k">template</span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">Duration</span><span class="o">></span>
<span class="n"><a href="../sys_time.html">sys_time</a></span><span class="o"><</span><span class="n"><a href="../common_type.html">common_type_t</a></span><span class="o"><</span><span class="n">Duration</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../duration_aliases.html">seconds</a></span><span class="o">>></span>
<span class="w"> </span><span class="n">to_sys</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../local_time.html">local_time</a></span><span class="o"><</span><span class="n">Duration</span><span class="o">>&</span><span class="w"> </span><span class="n">tp</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../choose.html">choose</a></span><span class="w"> </span><span class="n">z</span><span class="p">)</span><span class="w"> </span><span class="k">const</span><span class="p">;</span><span class="w"> </span><span class="c1">// (2) C++20</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p>ローカル時間からシステム時間に変換する。</p>
<ul>
<li>(1) : ローカル時間からシステム時間に変換する。あいまいなローカル時間もしくは存在しないローカル時間が指定された場合は<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出する</li>
<li>(2) : ローカル時間からシステム時間に変換する。あいまいなローカル時間が指定された場合は<code>z</code>で指定された方のシステム時間を返し、存在しないローカル時間が指定された場合は同じ時間点のシステム時間を返す</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="関数呼び出し式の評価結果となるオブジェクト・値">戻り値</a></h2>
<ul>
<li>(1) : 少なくとも秒以上の分解能で、タイムゾーンの規則に従ったUTCのシステム時間を返す</li>
<li>(2) : (1)に加え、<code>tp</code>からシステム時間への変換があいまいである場合、<code>z == <a href="../choose.html">choose::earliest</a></code>であるなら早い方のシステム時間候補を返し、<code>z == <a href="../choose.html">choose::latest</a></code>であるなら遅い方のシステム時間候補を返す。<code>tp</code>とUTC時間点の間に表現できる時間が存在しない場合、同じ時間点のシステム時間を返す</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a></h2>
<ul>
<li>(1) :<ul>
<li><code>tp</code>からシステム時間への変換があいまいである場合、<code><a href="../ambiguous_local_time.html">ambiguous_local_time</a></code><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出する</li>
<li><code>tp</code>とUTC時間点の間に表現できる時間が存在しない場合、<code><a href="../nonexistent_local_time.html">nonexistent_local_time</a></code><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出する</li>
</ul>
</li>
</ul>
<h2>備考</h2>
<ul>
<li>存在しないローカル時間およびあいまいなローカル時間は、サマータイムを採用しているタイムゾーンで生じる可能性がある<ul>
<li>存在しないローカル時間の例として、タイムゾーン<code>"America/New_York"</code>のローカル時刻 2016-03-13 02:30:00 は以下の隙間に位置するため存在しえない：<ul>
<li>2016-03-13 02:00:00 EST</li>
<li>2016-03-13 03:00:00 EDT</li>
<li>2016-03-13 07:00:00 UTC</li>
</ul>
</li>
<li>あいまいなローカル時間の例として、タイムゾーン<code>"America/New_York"</code>のローカル時刻 2016-11-06 01:30:00 は、以下のいずれかとなり、一意に決まらない：<ul>
<li>2016-11-06 05:30:00 UTC</li>
<li>2016-11-06 06:30:00 UTC</li>
</ul>
</li>
</ul>
</li>
</ul>
<h2>例</h2>
<p><div class="yata" id="d21f2154d6ef8aa8e4e4140be9aff80ffd0ab717"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../../cassert.html"><cassert></a></span>
<span class="cp">#include <a href="../../chrono.html"><chrono></a></span>
<span class="k">namespace</span><span class="w"> </span><span class="nn">chrono</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nn">std</span><span class="o">::</span><span class="nn">chrono</span><span class="p">;</span>
<span class="k">using</span><span class="w"> </span><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="o">::</span><span class="nn">chrono_literals</span><span class="p">;</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">now</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../system_clock.html">chrono::system_clock</a></span><span class="o">::</span><span class="n"><a href="../system_clock/now.html">now()</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../local_time.html">chrono::local_time</a></span><span class="w"> </span><span class="n">local_now</span><span class="p">{</span><span class="n">now</span><span class="p">.</span><span class="n"><a href="../time_point/time_since_epoch.html">time_since_epoch()</a></span><span class="p">};</span>
<span class="w"> </span><span class="n"><a href="../local_time.html">chrono::local_time</a></span><span class="w"> </span><span class="n">local_jst_now</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">local_now</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n"><a href="../duration/op_h.html">9h</a></span><span class="p">;</span>
<span class="w"> </span><span class="c1">// 日本のローカル時間をシステム時間 (UTCタイムゾーン) に変換する</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">chrono</span><span class="o">::</span><span class="n">time_zone</span><span class="o">*</span><span class="w"> </span><span class="n">jst</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../locate_zone.html">chrono::locate_zone</a></span><span class="p">(</span><span class="s">"Asia/Tokyo"</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../sys_time.html">chrono::sys_time</a></span><span class="w"> </span><span class="n">jst_to_utc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">jst</span><span class="o">-></span><span class="n"><span style="color:#ff0000">to_sys</span></span><span class="p">(</span><span class="n">local_jst_now</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n"><a href="../time_point/floor.html">chrono::floor</a></span><span class="o"><</span><span class="n"><a href="../duration_aliases.html">chrono::seconds</a></span><span class="o">></span><span class="p">(</span><span class="n">jst_to_utc</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n"><a href="../time_point/floor.html">chrono::floor</a></span><span class="o"><</span><span class="n"><a href="../duration_aliases.html">chrono::seconds</a></span><span class="o">></span><span class="p">(</span><span class="n">now</span><span class="p">));</span>
<span class="w"> </span><span class="c1">// ニューヨーク (EDTタイムゾーン) のローカル時間を、システム時間 (UTCタイムゾーン) に変換する。</span>
<span class="w"> </span><span class="c1">// ローカル時間2016-11-06 01:30:00 EDTに対応するシステム時間は、以下の2つがあり、一意に決まらない：</span>
<span class="w"> </span><span class="c1">// 2016-11-06 05:30:00 UTC</span>
<span class="w"> </span><span class="c1">// 2016-11-06 06:30:00 UTC</span>
<span class="w"> </span><span class="c1">// ここではlatestを指定することで、遅い時間 (06:30:00) を選択する</span>
<span class="w"> </span><span class="n"><a href="../local_time.html">chrono::local_time</a></span><span class="w"> </span><span class="n">edt_now</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../local_time.html">chrono::local_days</a></span><span class="p">{</span><span class="n"><a href="../year/op_y.html">2016y</a></span><span class="o">/</span><span class="mi">11</span><span class="o">/</span><span class="mi">6</span><span class="p">}</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n"><a href="../duration/op_h.html">1h</a></span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n"><a href="../duration/op_min.html">30min</a></span><span class="p">;</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">chrono</span><span class="o">::</span><span class="n">time_zone</span><span class="o">*</span><span class="w"> </span><span class="n">edt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../locate_zone.html">chrono::locate_zone</a></span><span class="p">(</span><span class="s">"America/New_York"</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// chooseを指定しない場合、あいまいなローカル時間を与えると例外が送出される</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">edt</span><span class="o">-></span><span class="n"><span style="color:#ff0000">to_sys</span></span><span class="p">(</span><span class="n">edt_now</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../cassert/assert.html">assert</a></span><span class="p">(</span><span class="nb">false</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n"><a href="../ambiguous_local_time.html">chrono::ambiguous_local_time</a></span><span class="o">&</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="n">what</span><span class="p">()</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">// chooseを指定した場合は、早い時間か遅い時間のどちらかを返す。</span>
<span class="w"> </span><span class="c1">// ここではlatestを指定しているため、遅い方の時間を返す</span>
<span class="w"> </span><span class="n"><a href="../sys_time.html">chrono::sys_time</a></span><span class="w"> </span><span class="n">edt_to_utc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">edt</span><span class="o">-></span><span class="n"><span style="color:#ff0000">to_sys</span></span><span class="p">(</span><span class="n">edt_now</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../choose.html">chrono::choose::latest</a></span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">edt_to_utc</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h3>出力例</h3>
<p><pre><code>2016-11-06 01:30:00 is ambiguous. It could be
2016-11-06 01:30:00 EDT == 2016-11-06 05:30:00 UTC or
2016-11-06 01:30:00 EST == 2016-11-06 06:30:00 UTC
2016-11-06 06:30:00
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++20</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../../implementation.html#clang">Clang</a>: 9.0 <span aria-label="未実装" role="img" title="未実装">❌</span></li>
<li><a href="../../../implementation.html#gcc">GCC</a>: 9.2 <span aria-label="未実装" role="img" title="未実装">❌</span>, 15.1 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../../implementation.html#visual_cpp">Visual C++</a>: 2019 Update 3 <span aria-label="未実装" role="img" title="未実装">❌</span></li>
</ul>
<h2>関連項目</h2>
<ul>
<li><code><a href="../local_info.html">local_info</a></code></li>
</ul></div>
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