From 28fa15c0aee4293a2180223359ad0b6bba61dcda Mon Sep 17 00:00:00 2001
From: Howard Hinnant <howard.hinnant@gmail.com>
Date: Sat, 12 Aug 2017 22:32:35 -0400
Subject: [PATCH] Template zoned_time on TimeZonePtr

---
 d0355r4.html | 387 +++++++++++++++++++++++++++++++++------------------
 1 file changed, 249 insertions(+), 138 deletions(-)

diff --git a/d0355r4.html b/d0355r4.html
index d719ace..6a569d4 100644
--- a/d0355r4.html
+++ b/d0355r4.html
@@ -59,6 +59,7 @@ Document number: D0355R4<br>
 <h3>Changes since <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0355r3.html">R3</a></h3>
 
 <ul>
+<li>Template <code>zoned_time</code> on <code>TimeZonePtr</code>.</li>
 <li>Give <code>weekday_indexed</code> a defaulted default constructor.</li>
 <li>Make <code>from_stream</code> and <code>to_stream</code> customization points.</li>
 <li>Make the database singleton a singly linked list of <code>tzdb</code> with
@@ -794,6 +795,7 @@ which is equal to <code>nullptr</code>.
         <a href="#time.timezone.exception">[time.timezone.exception]</a>
         <a href="#time.timezone.info">[time.timezone.info]</a>
         <a href="#time.timezone.time_zone">[time.timezone.time_zone]</a>
+        <a href="#time.timezone.zoned_traits">[time.timezone.zoned_traits]</a>
         <a href="#time.timezone.zoned_time">[time.timezone.zoned_time]</a>
         <a href="#time.timezone.leap">[time.timezone.leap]</a>
         <a href="#time.timezone.link">[time.timezone.link]</a>
@@ -1450,25 +1452,29 @@ bool operator&lt;=(const time_zone&amp; x, const time_zone&amp; y) noexcept;
 bool operator&gt;=(const time_zone&amp; x, const time_zone&amp; y) noexcept;
 
 // zoned_time
-template &lt;class Duration&gt; class zoned_time;
+template &lt;class Duration, class TimeZonePtr = const time_zone*&gt; class zoned_time;
 
 using zoned_seconds = zoned_time&lt;seconds&gt;;
 
-template &lt;class Duration1, class Duration2&gt;
+template &lt;class Duration1, class Duration2, class TimeZonePtr&gt;
     bool
-    operator==(const zoned_time&lt;Duration1&gt;&amp; x, const zoned_time&lt;Duration2&gt;&amp; y);
+    operator==(const zoned_time&lt;Duration1, TimeZonePtr&gt;&amp; x,
+               const zoned_time&lt;Duration2, TimeZonePtr&gt;&amp; y);
 
-template &lt;class Duration1, class Duration2&gt;
+template &lt;class Duration1, class Duration, class TimeZonePtr2&gt;
     bool
-    operator!=(const zoned_time&lt;Duration1&gt;&amp; x, const zoned_time&lt;Duration2&gt;&amp; y);
+    operator!=(const zoned_time&lt;Duration1, TimeZonePtr&gt;&amp; x,
+               const zoned_time&lt;Duration2, TimeZonePtr&gt;&amp; y);
 
-template &lt;class charT, class traits, class Duration&gt;
+template &lt;class charT, class traits, class Duration, class TimeZonePtr&gt;
     basic_ostream&lt;charT, traits&gt;&amp;
-    operator&lt;&lt;(basic_ostream&lt;charT, traits&gt;&amp; os, const zoned_time&lt;Duration&gt;& t);
+    operator&lt;&lt;(basic_ostream&lt;charT, traits&gt;&amp; os,
+               const zoned_time&lt;Duration, TimeZonePtr&gt;& t);
 
-template &lt;class charT, class traits, class Duration&gt;
+template &lt;class charT, class traits, class Duration, class TimeZonePtr&gt;
     basic_ostream&lt;charT, traits&gt;&amp;
-    to_stream(basic_ostream&lt;charT, traits&gt;&amp; os, const charT* fmt, const zoned_time&lt;Duration&gt;&amp; tp);
+    to_stream(basic_ostream&lt;charT, traits&gt;&amp; os, const charT* fmt,
+              const zoned_time&lt;Duration, TimeZonePtr&gt;&amp; tp);
 
 // format
 
@@ -9784,7 +9790,46 @@ bool operator&gt;=(const time_zone&amp; x, const time_zone&amp; y) noexcept;
 </p>
 </blockquote>
 
-<a name="time.timezone.zoned_time"></a><h3>23.17.12.5 Class <code>zoned_time</code> [time.timezone.zoned_time]</h3>
+<a name="time.timezone.zoned_traits"></a><h3>23.17.12.5 Class <code>zoned_traits</code> [time.timezone.zoned_traits]</h3>
+
+<p>
+<code>zoned_traits</code> provides a means for customizing the behavior of
+<code>zoned_time&lt;Duration, TimeZonePtr</code> for the
+<code>zoned_time</code> default constructor, and constructors taking
+<code>string_view</code>.  A specialization for <code>const time_zone*</code>
+is provided by the implementation.
+</p>
+
+<pre>
+template &lt;class T&gt; struct zoned_traits {};
+
+template &lt;&gt;
+struct zoned_traits&lt;const time_zone*&gt;
+{
+    static const time_zone* default_zone();
+    static const time_zone* locate_zone(string_view name);
+};
+</pre>
+
+<pre>
+static const time_zone* zoned_traits&lt;const time_zone*&gt;::default_zone();
+</pre>
+<blockquote>
+<p>
+<i>Returns:</i> <code>date::locate_zone("UTC")</code>.
+</p>
+</blockquote>
+
+<pre>
+static const time_zone* zoned_traits&lt;const time_zone*&gt;::locate_zone(string_view name);
+</pre>
+<blockquote>
+<p>
+<i>Returns:</i> <code>date::locate_zone(name)</code>.
+</p>
+</blockquote>
+
+<a name="time.timezone.zoned_time"></a><h3>23.17.12.6 Class <code>zoned_time</code> [time.timezone.zoned_time]</h3>
 
 <p>
 <code>zoned_time</code> represents a logical paring of <code>time_zone</code> and a
@@ -9792,14 +9837,14 @@ bool operator&gt;=(const time_zone&amp; x, const time_zone&amp; y) noexcept;
 </p>
 
 <pre>
-template &lt;class Duration&gt;
+template &lt;class Duration, class TimeZonePtr = const time_zone*&gt;
 class zoned_time
 {
 public:
     using duration = common_type_t&lt;Duration, seconds&gt;;
 
 private:
-    const time_zone*   zone_;  // exposition only
+    TimeZonePtr        zone_;  // exposition only
     sys_time&lt;duration&gt; tp_;    // exposition only
 
 public:
@@ -9808,24 +9853,24 @@ public:
     zoned_time&amp; operator=(const zoned_time&amp;) = default;
 
              zoned_time(const sys_time&lt;Duration&gt;&amp; st);
-    explicit zoned_time(const time_zone* z);
+    explicit zoned_time(TimeZonePtr z);
     explicit zoned_time(string_view name);
 
     template &lt;class Duration2&gt;
         zoned_time(const zoned_time&lt;Duration2&gt;&amp; zt) noexcept;
 
-    zoned_time(const time_zone* z, const local_time&lt;Duration&gt;&amp; tp);
-    zoned_time(string_view   name, const local_time&lt;Duration&gt;&amp; tp);
-    zoned_time(const time_zone* z, const local_time&lt;Duration&gt;&amp; tp, choose c);
-    zoned_time(string_view   name, const local_time&lt;Duration&gt;&amp; tp, choose c);
+    zoned_time(TimeZonePtr z,    const sys_time&lt;Duration&gt;&amp; st);
+    zoned_time(string_view name, const sys_time&lt;Duration&gt;&amp; st);
 
-    zoned_time(const time_zone* z, const zoned_time&lt;Duration&gt;&amp; zt);
-    zoned_time(string_view   name, const zoned_time&lt;Duration&gt;&amp; zt);
-    zoned_time(const time_zone* z, const zoned_time&lt;Duration&gt;&amp; zt, choose);
-    zoned_time(string_view   name, const zoned_time&lt;Duration&gt;&amp; zt, choose);
+    zoned_time(TimeZonePtr z,    const local_time&lt;Duration&gt;&amp; tp);
+    zoned_time(string_view name, const local_time&lt;Duration&gt;&amp; tp);
+    zoned_time(TimeZonePtr z,    const local_time&lt;Duration&gt;&amp; tp, choose c);
+    zoned_time(string_view name, const local_time&lt;Duration&gt;&amp; tp, choose c);
 
-    zoned_time(const time_zone* z, const sys_time&lt;Duration&gt;&amp; st);
-    zoned_time(string_view   name, const sys_time&lt;Duration&gt;&amp; st);
+    zoned_time(TimeZonePtr z,    const zoned_time&lt;Duration&gt;&amp; zt);
+    zoned_time(string_view name, const zoned_time&lt;Duration&gt;&amp; zt);
+    zoned_time(TimeZonePtr z,    const zoned_time&lt;Duration&gt;&amp; zt, choose);
+    zoned_time(string_view name, const zoned_time&lt;Duration&gt;&amp; zt, choose);
 
     zoned_time&amp; operator=(const sys_time&lt;Duration&gt;&amp; st);
     zoned_time&amp; operator=(const local_time&lt;Duration&gt;&amp; ut);
@@ -9833,43 +9878,61 @@ public:
              operator sys_time&lt;duration&gt;()   const;
     explicit operator local_time&lt;duration&gt;() const;
 
-    const time_zone*     get_time_zone()  const;
+    TimeZonePtr          get_time_zone()  const;
     local_time&lt;duration&gt; get_local_time() const;
     sys_time&lt;duration&gt;   get_sys_time()   const;
     sys_info             get_info()       const;
 };
 
-template &lt;class Duration1, class Duration2&gt;
+template &lt;class Duration1, class Duration2, class TimeZonePtr&gt;
 bool
-operator==(const zoned_time&lt;Duration1&gt;&amp; x, const zoned_time&lt;Duration2&gt;&amp; y);
+operator==(const zoned_time&lt;Duration1, TimeZonePtr&gt;&amp; x,
+           const zoned_time&lt;Duration2, TimeZonePtr&gt;&amp; y);
 
-template &lt;class Duration1, class Duration2&gt;
+template &lt;class Duration1, class Duration2, class TimeZonePtr&gt;
 bool
-operator!=(const zoned_time&lt;Duration1&gt;&amp; x, const zoned_time&lt;Duration2&gt;&amp; y);
+operator!=(const zoned_time&lt;Duration1, TimeZonePtr&gt;&amp; x,
+           const zoned_time&lt;Duration2, TimeZonePtr&gt;&amp; y);
 
-template &lt;class charT, class traits, class Duration&gt;
+template &lt;class charT, class traits, class Duration, class TimeZonePtr&gt;
     basic_ostream&lt;charT, traits&gt;&amp;
-    operator&lt;&lt;(basic_ostream&lt;charT, traits&gt;&amp; os, const zoned_time&lt;Duration&gt;& t);
+    operator&lt;&lt;(basic_ostream&lt;charT, traits&gt;&amp; os,
+               const zoned_time&lt;Duration, TimeZonePtr&gt;& t);
 
-template &lt;class charT, class traits, class Duration&gt;
+template &lt;class charT, class traits, class Duration, class TimeZonePtr&gt;
     basic_ostream&lt;charT, traits&gt;&amp;
-    to_stream(basic_ostream&lt;charT, traits&gt;&amp; os, const charT* fmt, const zoned_time&lt;Duration&gt;&amp; tp);
+    to_stream(basic_ostream&lt;charT, traits&gt;&amp; os, const charT* fmt,
+              const zoned_time&lt;Duration, TimeZonePtr&gt;&amp; tp);
+
+zoned_time()
+    -&gt; zoned_time&lt;seconds&gt;;
 
 template &lt;class Duration&gt;
     zoned_time(sys_time&lt;Duration&gt;)
         -&gt; zoned_time&lt;common_type_t&lt;Duration, seconds&gt;&gt;;
 
-template &lt;class Zone, class Duration&gt;
-    zoned_time(Zone, sys_time&lt;Duration&gt;)
-        -&gt; zoned_time&lt;common_type_t&lt;Duration, seconds&gt;&gt;;
+template &lt;class TimeZonePtr, class Duration&gt;
+    zoned_time(TimeZonePtr, sys_time&lt;Duration&gt;)
+        -&gt; zoned_time&lt;common_type_t&lt;Duration, seconds&gt;, TimeZonePtr&gt;;
 
-template &lt;class Zone, class Duration&gt;
-    zoned_time(Zone, local_time&lt;Duration&gt;, choose = choose::earliest)
-        -&gt; zoned_time&lt;common_type_t&lt;Duration, seconds&gt;&gt;;
+template &lt;class TimeZonePtr, class Duration&gt;
+    zoned_time(TimeZonePtr, local_time&lt;Duration&gt;, choose = choose::earliest)
+        -&gt; zoned_time&lt;common_type_t&lt;Duration, seconds&gt;, TimeZonePtr&gt;;
 
-template &lt;class Zone, class Duration&gt;
-    zoned_time(Zone, zoned_time&lt;Duration&gt;, choose = choose::earliest)
-        -&gt; zoned_time&lt;common_type_t&lt;Duration, seconds&gt;&gt;;
+template &lt;class TimeZonePtr, class Duration&gt;
+    zoned_time(TimeZonePtr, zoned_time&lt;Duration&gt;, choose = choose::earliest)
+        -&gt; zoned_time&lt;common_type_t&lt;Duration, seconds&gt;, TimeZonePtr&gt;;
+
+zoned_time(string_view)
+    -&gt; zoned_time&lt;seconds&gt;;
+
+template &lt;class Duration&gt;
+zoned_time(string_view, sys_time&lt;Duration&gt;)
+    -&gt; zoned_time&lt;common_type_t&lt;Duration, seconds&gt;&gt;;
+
+template &lt;class Duration&gt;
+zoned_time(string_view, local_time&lt;Duration&gt;, choose = choose::earliest)
+    -&gt; zoned_time&lt;common_type_t&lt;Duration, seconds&gt;&gt;;
 </pre>
 
 <p>
@@ -9879,19 +9942,23 @@ and is not ambiguous.
 </p>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time();
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time();
 </pre>
 <blockquote>
 <p>
-<i>Effects:</i> Constructs a <code>zoned_time</code> <code>zt</code> such that
-<code>zt.get_time_zone()-&gt;name() == "UTC"</code>, and
-<code>zt.get_sys_time() == sys_seconds{}</code>.
+<i>Remarks:</i>  This constructor does not participate in overload resolution unless
+the expression <code>zoned_traits&lt;TimeZonePtr&gt;::default_zone()</code> is well formed.
+</p>
+<p>
+<i>Effects:</i> Constructs a <code>zoned_time</code> by initializing
+<code>zone_</code> with <code>zoned_traits&lt;TimeZonePtr&gt;::default_zone()</code> and
+default constructing <code>tp_</code>.
 </p>
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(const zoned_time&amp;) = default;
-zoned_time&lt;Duration&gt;&amp; zoned_time&lt;Duration&gt;::operator=(const zoned_time&amp;) = default;
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(const zoned_time&amp;) = default;
+zoned_time&lt;Duration, TimeZonePtr&gt;&amp; zoned_time&lt;Duration&gt;::operator=(const zoned_time&amp;) = default;
 </pre>
 <blockquote>
 <p>
@@ -9904,45 +9971,53 @@ members.
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(const sys_time&lt;Duration&gt;&amp; st);
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(const sys_time&lt;Duration&gt;&amp; st);
 </pre>
 <blockquote>
 <p>
-<i>Effects:</i> Constructs a <code>zoned_time</code> <code>zt</code> such that
-<code>zt.get_time_zone()-&gt;name() == "UTC"</code>, and
-<code>zt.get_sys_time() == st</code>.
+<i>Remarks:</i>  This constructor does not participate in overload resolution unless
+the expression <code>zoned_traits&lt;TimeZonePtr&gt;::default_zone()</code> is well formed.
+</p>
+<p>
+<i>Effects:</i> Constructs a <code>zoned_time</code> by initializing
+<code>zone_</code> with <code>zoned_traits&lt;TimeZonePtr&gt;::default_zone()</code> and
+<code>tp_</code> with <code>st</code>.
 </p>
 </blockquote>
 
 <pre>
-explicit zoned_time&lt;Duration&gt;::zoned_time(const time_zone* z);
+explicit zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(TimeZonePtr z);
 </pre>
 <blockquote>
 <p>
 <i>Requires:</i> <code>z</code> refers to a valid <code>time_zone</code>.
 </p>
 <p>
-<i>Effects:</i> Constructs a <code>zoned_time</code> <code>zt</code> such that
-<code>zt.get_time_zone() == z</code>, and
-<code>zt.get_sys_time() == sys_seconds{}</code>.
+<i>Effects:</i> Constructs a <code>zoned_time</code> initializing <code>zone_</code>
+with <code>std::move(z)</code>.
 </p>
 </blockquote>
 
 <pre>
-explicit zoned_time&lt;Duration&gt;::zoned_time(string_view name);
+explicit zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(string_view name);
 </pre>
 <blockquote>
 <p>
-<i>Effects:</i> Equivalent to construction with <code>locate_zone(name)</code>.
+<i>Remarks:</i>  This constructor does not participate in overload resolution unless
+the expression <code>zoned_traits&lt;TimeZonePtr&gt;::locate_zone(string_view{})</code>
+is well formed and <code>zoned_time</code> is constructible from the return type of
+<code>zoned_traits&lt;TimeZonePtr&gt;::locate_zone(string_view{})</code>.
 </p>
 <p>
-<i>Throws:</i> Any exception propagating out of <code>locate_zone(name)</code>.
+<i>Effects:</i> Constructs a <code>zoned_time</code> by initializing
+<code>zone_</code> with <code>zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name)</code>
+and default constructing <code>tp_</code>.
 </p>
 </blockquote>
 
 <pre>
-template &lt;class Duration2&gt;
-    zoned_time&lt;Duration&gt;::zoned_time(const zoned_time&lt;Duration2&gt;&amp; y) noexcept;
+template &lt;class Duration2, TimeZonePtr&gt;
+    zoned_time&lt;Duration&gt;::zoned_time(const zoned_time&lt;Duration2, TimeZonePtr&gt;&amp; y) noexcept;
 </pre>
 <blockquote>
 <p>
@@ -9957,87 +10032,153 @@ template &lt;class Duration2&gt;
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(const time_zone* z, const local_time&lt;Duration&gt;&amp; tp);
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(TimeZonePtr z, const sys_time&lt;Duration&gt;&amp; st);
 </pre>
 <blockquote>
 <p>
 <i>Requires:</i> <code>z</code> refers to a valid <code>time_zone</code>.
 </p>
 <p>
-<i>Effects:</i> Constructs a <code>zoned_time</code> <code>zt</code> such that
-<code>zt.get_time_zone()-&gt; == z</code>, and <code>zt.get_local_time() == tp</code>.
-</p>
-<p>
-<i>Throws:</i> Any exception that <code>z-&gt;to_sys(tp)</code> would throw.
+<i>Effects:</i> Constructs a <code>zoned_time</code> by initializing <code>zone_</code>
+with <code>std::move(z)</code> and <code>tp_</code> with <code>st</code>.
 </p>
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(string_view name, const local_time&lt;Duration&gt;&amp; tp);
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(string_view name, const sys_time&lt;Duration&gt;&amp; st);
 </pre>
 <blockquote>
 <p>
-<i>Effects:</i> Equivalent to construction with <code>{locate_zone(name), tp}</code>.
+<i>Remarks:</i> This constructor does not participate in overload resolution unless
+<code>zoned_time</code> is constructible from the return type of
+<code>zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name)</code> and <code>st</code>.
+</p>
+<p>
+<i>Effects:</i> Equivalent to construction with <code>{zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name), st}</code>.
 </p>
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(const time_zone* z, const local_time&lt;Duration&gt;&amp; tp, choose c);
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(TimeZonePtr z, const local_time&lt;Duration&gt;&amp; tp);
 </pre>
 <blockquote>
 <p>
 <i>Requires:</i> <code>z</code> refers to a valid <code>time_zone</code>.
 </p>
 <p>
-<i>Effects:</i> Constructs a <code>zoned_time</code> <code>zt</code> such that
-<code>zt.get_time_zone()-&gt; == z</code>, and
-<code>zt.get_sys_time() == z-&gt;to_sys(tp, c)</code>.
+<i>Remarks:</i> This constructor does not participate in overload resolution unless
+<code>declval&lt;TimeZonePtr&amp;&gt;()-&gt;to_sys(local_time&lt;Duration&gt;{})</code>
+is convertible to <code>sys_time&lt;duration&gt;</code>.
+</p>
+<p>
+<i>Effects:</i> Constructs a <code>zoned_time</code> by initializing <code>zone_</code>
+with <code>std::move(z)</code> and <code>tp_</code> with <code>zone_-&gt;to_sys(t)</code>.
 </p>
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(string_view name, const local_time&lt;Duration&gt;&amp; tp, choose c);
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(string_view name, const local_time&lt;Duration&gt;&amp; tp);
 </pre>
 <blockquote>
 <p>
-<i>Effects:</i> Equivalent to construction with <code>{locate_zone(name), tp, c}</code>.
+<i>Remarks:</i> This constructor does not participate in overload resolution unless
+<code>zoned_time</code> is constructible from the return type of
+<code>zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name)</code> and <code>tp</code>.
+</p>
+<p>
+<i>Effects:</i> Equivalent to construction with <code>{zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name), tp}</code>.
 </p>
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(const time_zone* z, const zoned_time&lt;Duration&gt;&amp; y);
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(TimeZonePtr z, const local_time&lt;Duration&gt;&amp; tp, choose c);
 </pre>
 <blockquote>
 <p>
 <i>Requires:</i> <code>z</code> refers to a valid <code>time_zone</code>.
 </p>
 <p>
-<i>Effects:</i> Constructs a <code>zoned_time</code> <code>zt</code> such that
-<code>zt.get_time_zone()-&gt; == z</code>, and
-<code>zt.get_sys_time() == y.get_sys_time()</code>.
+<i>Remarks:</i> This constructor does not participate in overload resolution unless
+<code>decltype(declval&lt;TimeZonePtr&amp;&gt;()-&gt;to_sys(local_time&lt;Duration&gt;{}, choose::earliest))</code>
+is convertible to <code>sys_time&lt;duration&gt;</code>.
+</p>
+<p>
+<i>Effects:</i> Constructs a <code>zoned_time</code> by initializing <code>zone_</code>
+with <code>std::move(z)</code> and <code>tp_</code> with <code>zone_-&gt;to_sys(t, c)</code>.
 </p>
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(string_view name, const zoned_time&lt;Duration&gt;&amp; y);
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(string_view name, const local_time&lt;Duration&gt;&amp; tp, choose c);
 </pre>
 <blockquote>
 <p>
-<i>Effects:</i> Equivalent to construction with <code>{locate_zone(name), y}</code>.
+<i>Remarks:</i> This constructor does not participate in overload resolution unless
+<code>zoned_time</code> is constructible from the return type of
+<code>zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name)</code>,
+<code>local_time&lt;Duration&gt;</code> and <code>choose</code>.
+</p>
+<p>
+<i>Effects:</i> Equivalent to construction with
+<code>{zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name), tp, c}</code>.
 </p>
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(const time_zone* z, const zoned_time&lt;Duration&gt;&amp; y, choose);
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(TimeZonePtr z, const zoned_time&lt;Duration&gt;&amp; y);
 </pre>
 <blockquote>
 <p>
 <i>Requires:</i> <code>z</code> refers to a valid <code>time_zone</code>.
 </p>
 <p>
-<i>Effects:</i> Constructs a <code>zoned_time</code> <code>zt</code> such that
-<code>zt.get_time_zone()-&gt; == z</code>, and
-<code>zt.get_sys_time() == y.get_sys_time()</code>.
+<i>Effects:</i> Constructs a <code>zoned_time</code> by initializing <code>zone_</code>
+with <code>std::move(z)</code> and <code>tp_</code> with <code>z.tp_</code>.
+</p>
+</blockquote>
+
+<pre>
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(string_view name, const zoned_time&lt;Duration&gt;&amp; y);
+</pre>
+<blockquote>
+<p>
+<i>Remarks:</i> This constructor does not participate in overload resolution unless
+<code>zoned_time</code> is constructible from the return type of
+<code>zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name)</code>
+and <code>zoned_time</code>.
+</p>
+<p>
+<i>Effects:</i> Equivalent to construction with
+<code>{zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name), y}</code>.
+</p>
+</blockquote>
+
+<pre>
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(TimeZonePtr z, const zoned_time&lt;Duration&gt;&amp; y, choose);
+</pre>
+<blockquote>
+<p>
+<i>Requires:</i> <code>z</code> refers to a valid <code>time_zone</code>.
+</p>
+<p>
+<i>Effects:</i> Equivalent to construction with <code>{z, y}</code>.
+</p>
+<i>Note:</i> The <code>choose</code> parameter is allowed here, but has no impact.
+</p>
+</blockquote>
+
+<pre>
+zoned_time&lt;Duration, TimeZonePtr&gt;::zoned_time(string_view name, const zoned_time&lt;Duration&gt;&amp; y, choose c);
+</pre>
+<blockquote>
+<p>
+<i>Remarks:</i> This constructor does not participate in overload resolution unless
+<code>zoned_time</code> is constructible from the return type of
+<code>zoned_traits&lt;TimeZonePtr&gt;::locate_zone(name)</code>, <code>zoned_time</code>,
+and <code>choose</code>.
+</p>
+<p>
+<i>Effects:</i> Equivalent to construction with <code>{locate_zone(name), y, c}</code>.
 </p>
 <p>
 <i>Note:</i> The <code>choose</code> parameter is allowed here, but has no impact.
@@ -10045,41 +10186,7 @@ zoned_time&lt;Duration&gt;::zoned_time(const time_zone* z, const zoned_time&lt;D
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::zoned_time(string_view name, const zoned_time&lt;Duration&gt;&amp; y, choose);
-</pre>
-<blockquote>
-<p>
-<i>Effects:</i> Equivalent to construction with <code>{locate_zone(name), y}</code>.
-</p>
-<p>
-<i>Note:</i> The <code>choose</code> parameter is allowed here, but has no impact.
-</p>
-</blockquote>
-
-<pre>
-zoned_time&lt;Duration&gt;::zoned_time(const time_zone* z, const sys_time&lt;Duration&gt;&amp; st);
-</pre>
-<blockquote>
-<p>
-<i>Requires:</i> <code>z</code> refers to a valid <code>time_zone</code>.
-</p>
-<p>
-<i>Effects:</i> Constructs a <code>zoned_time</code> <code>zt</code> such that
-<code>zt.get_time_zone()-&gt; == z</code>, and <code>zt.get_sys_time() == st</code>.
-</p>
-</blockquote>
-
-<pre>
-zoned_time&lt;Duration&gt;::zoned_time(string_view name, const sys_time&lt;Duration&gt;&amp; st);
-</pre>
-<blockquote>
-<p>
-<i>Effects:</i> Equivalent to construction with <code>{locate_zone(name), st}</code>.
-</p>
-</blockquote>
-
-<pre>
-zoned_time&lt;Duration&gt;&amp; zoned_time&lt;Duration&gt;::operator=(const sys_time&lt;Duration&gt;&amp; st);
+zoned_time&lt;Duration, TimeZonePtr&gt;&amp; zoned_time&lt;Duration, TimeZonePtr&gt;::operator=(const sys_time&lt;Duration&gt;&amp; st);
 </pre>
 <blockquote>
 <p>
@@ -10092,7 +10199,7 @@ no effect on the return value of <code>get_time_zone()</code>.
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;&amp; zoned_time&lt;Duration&gt;::operator=(const local_time&lt;Duration&gt;&amp; lt);
+zoned_time&lt;Duration, TimeZonePtr&gt;&amp; zoned_time&lt;Duration, TimeZonePtr&gt;::operator=(const local_time&lt;Duration&gt;&amp; lt);
 </pre>
 <blockquote>
 <p>
@@ -10105,7 +10212,7 @@ no effect on the return value of <code>get_time_zone()</code>.
 </blockquote>
 
 <pre>
-zoned_time&lt;Duration&gt;::operator sys_time&lt;duration&gt;() const;
+zoned_time&lt;Duration, TimeZonePtr&gt;::operator sys_time&lt;duration&gt;() const;
 </pre>
 <blockquote>
 <p>
@@ -10114,7 +10221,7 @@ zoned_time&lt;Duration&gt;::operator sys_time&lt;duration&gt;() const;
 </blockquote>
 
 <pre>
-explicit zoned_time&lt;Duration&gt;::operator local_time&lt;duration&gt;() const;
+explicit zoned_time&lt;Duration, TimeZonePtr&gt;::operator local_time&lt;duration&gt;() const;
 </pre>
 <blockquote>
 <p>
@@ -10123,7 +10230,7 @@ explicit zoned_time&lt;Duration&gt;::operator local_time&lt;duration&gt;() const
 </blockquote>
 
 <pre>
-const time_zone* zoned_time&lt;Duration&gt;::get_time_zone() const;
+TimeZonePtr zoned_time&lt;Duration, TimeZonePtr&gt;::get_time_zone() const;
 </pre>
 <blockquote>
 <p>
@@ -10132,7 +10239,7 @@ const time_zone* zoned_time&lt;Duration&gt;::get_time_zone() const;
 </blockquote>
 
 <pre>
-local_time&lt;typename zoned_time&lt;Duration&gt;::duration&gt; zoned_time&lt;Duration&gt;::get_local_time() const;
+local_time&lt;typename zoned_time&lt;Duration, TimeZonePtr&gt;::duration&gt; zoned_time&lt;Duration, TimeZonePtr&gt;::get_local_time() const;
 </pre>
 <blockquote>
 <p>
@@ -10141,7 +10248,7 @@ local_time&lt;typename zoned_time&lt;Duration&gt;::duration&gt; zoned_time&lt;Du
 </blockquote>
 
 <pre>
-sys_time&lt;typename zoned_time&lt;Duration&gt;::duration&gt; zoned_time&lt;Duration&gt;::get_sys_time() const;
+sys_time&lt;typename zoned_time&lt;Duration, TimeZonePtr&gt;::duration&gt; zoned_time&lt;Duration, TimeZonePtr&gt;::get_sys_time() const;
 </pre>
 <blockquote>
 <p>
@@ -10150,7 +10257,7 @@ sys_time&lt;typename zoned_time&lt;Duration&gt;::duration&gt; zoned_time&lt;Dura
 </blockquote>
 
 <pre>
-sys_info zoned_time&lt;Duration&gt;::get_info() const;
+sys_info zoned_time&lt;Duration, TimeZonePtr&gt;::get_info() const;
 </pre>
 <blockquote>
 <p>
@@ -10159,9 +10266,10 @@ sys_info zoned_time&lt;Duration&gt;::get_info() const;
 </blockquote>
 
 <pre>
-template &lt;class Duration1, class Duration2&gt;
+template &lt;class Duration1, class Duration2, class TimeZonePtr&gt;
 bool
-operator==(const zoned_time&lt;Duration1&gt;&amp; x, const zoned_time&lt;Duration2&gt;&amp; y);
+operator==(const zoned_time&lt;Duration1, TimeZonePtr&gt;&amp; x,
+           const zoned_time&lt;Duration2, TimeZonePtr&gt;&amp; y);
 </pre>
 <blockquote>
 <p>
@@ -10170,9 +10278,10 @@ operator==(const zoned_time&lt;Duration1&gt;&amp; x, const zoned_time&lt;Duratio
 </blockquote>
 
 <pre>
-template &lt;class Duration1, class Duration2&gt;
+template &lt;class Duration1, class Duration2, class TimeZonePtr&gt;
 bool
-operator!=(const zoned_time&lt;Duration1&gt;&amp; x, const zoned_time&lt;Duration2&gt;&amp; y);
+operator!=(const zoned_time&lt;Duration1, TimeZonePtr&gt;&amp; x,
+           const zoned_time&lt;Duration2, TimeZonePtr&gt;&amp; y);
 </pre>
 <blockquote>
 <p>
@@ -10181,9 +10290,10 @@ operator!=(const zoned_time&lt;Duration1&gt;&amp; x, const zoned_time&lt;Duratio
 </blockquote>
 
 <pre>
-template &lt;class charT, class traits, class Duration&gt;
+template &lt;class charT, class traits, class Duration, class TimeZonePtr&gt;
 basic_ostream&lt;charT, traits&gt;&
-operator&lt;&lt;(basic_ostream&lt;charT, traits&gt;& os, const zoned_time&lt;Duration&gt;&amp; t)
+operator&lt;&lt;(basic_ostream&lt;charT, traits&gt;& os,
+           const zoned_time&lt;Duration, TimeZonePtr&gt;&amp; t)
 </pre>
 <blockquote>
 <p>
@@ -10196,9 +10306,10 @@ and the value returned from <code>t.get_local_time()</code>.
 </blockquote>
 
 <pre>
-template &lt;class charT, class traits, class Duration&gt;
+template &lt;class charT, class traits, class Duration, class TimeZonePtr&gt;
 basic_ostream&lt;charT, traits&gt;&amp;
-to_stream(basic_ostream&lt;charT, traits&gt;&amp; os, const charT* fmt, const zoned_time&lt;Duration&gt;&amp; tp);
+to_stream(basic_ostream&lt;charT, traits&gt;&amp; os, const charT* fmt,
+          const zoned_time&lt;Duration, TimeZonePtr&gt;&amp; tp);
 </pre>
 
 <blockquote>
@@ -10218,12 +10329,12 @@ which for exposition purposes will be referred to as <code>info</code>.  Then ca
 </blockquote>
 
 <p class = note>
-Add a new section 23.17.12.10 leap [time.timezone.leap]:
+Add a new section 23.17.12.7 leap [time.timezone.leap]:
 </p>
 
 <blockquote>
 
-<a name="time.timezone.leap"></a><h3>23.17.12.10 class <code>leap</code> [time.timezone.leap]</h3>
+<a name="time.timezone.leap"></a><h3>23.17.12.7 class <code>leap</code> [time.timezone.leap]</h3>
 
 
 <pre>
@@ -10494,12 +10605,12 @@ template &lt;class Duration&gt; bool operator&gt;=(const sys_time&lt;Duration&gt
 </blockquote>
 
 <p class = note>
-Add a new section 23.17.12.11 link [time.timezone.link]:
+Add a new section 23.17.12.8 link [time.timezone.link]:
 </p>
 
 <blockquote>
 
-<a name="time.timezone.link"></a><h3>23.17.12.11 class <code>link</code> [time.timezone.link]</h3>
+<a name="time.timezone.link"></a><h3>23.17.12.8 class <code>link</code> [time.timezone.link]</h3>
 
 <pre>
 class link