git init

src/date/chrono_io.h

@@ -0,0 +1,34 @@
+#ifndef CHRONO_IO_H
+#define CHRONO_IO_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2016, 2017 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// Our apologies.  When the previous paragraph was written, lowercase had not yet
+// been invented (that would involve another several millennia of evolution).
+// We did not mean to shout.
+
+// This functionality has moved to "date.h"
+
+#include "date.h"
+
+#endif  // CHRONO_IO_H

src/date/ptz.h

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+#ifndef PTZ_H
+#define PTZ_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2017 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// This header allows Posix-style time zones as specified for TZ here:
+// http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
+//
+// Posix::time_zone can be constructed with a posix-style string and then used in
+// a zoned_time like so:
+//
+// zoned_time<system_clock::duration, Posix::time_zone> zt{"EST5EDT,M3.2.0,M11.1.0",
+//                                                         system_clock::now()};
+// or:
+//
+// Posix::time_zone tz{"EST5EDT,M3.2.0,M11.1.0"};
+// zoned_time<system_clock::duration, Posix::time_zone> zt{tz, system_clock::now()};
+//
+// In C++17 CTAD simplifies this to:
+//
+// Posix::time_zone tz{"EST5EDT,M3.2.0,M11.1.0"};
+// zoned_time zt{tz, system_clock::now()};
+//
+// Extension to the Posix rules to allow a constant daylight saving offset:
+//
+// If the rule set is missing (everything starting with ','), then
+// there must be exactly one abbreviation (std or daylight) with
+// length 3 or greater, and that will be used as the constant offset. If
+// there are two, the std abbreviation is silently set to "", and the
+// result is constant daylight saving. If there are zero abbreviations
+// with no rule set, an exception is thrown.
+//
+// Example:
+// "EST5" yields a constant offset of -5h with 0h save and "EST abbreviation.
+// "5EDT" yields a constant offset of -4h with 1h save and "EDT" abbreviation.
+// "EST5EDT" and "5EDT4" are both equal to "5EDT".
+//
+// Note, Posix-style time zones are not recommended for all of the reasons described here:
+// https://stackoverflow.com/tags/timezone/info
+//
+// They are provided here as a non-trivial custom time zone example, and if you really
+// have to have Posix time zones, you're welcome to use this one.
+
+#include "date/tz.h"
+#include <algorithm>
+#include <cctype>
+#include <ostream>
+#include <string>
+
+namespace Posix
+{
+
+namespace detail
+{
+
+#if HAS_STRING_VIEW
+
+using string_t = std::string_view;
+
+#else  // !HAS_STRING_VIEW
+
+using string_t = std::string;
+
+#endif  // !HAS_STRING_VIEW
+
+class rule;
+
+void throw_invalid(const string_t& s, unsigned i, const string_t& message);
+unsigned read_date(const string_t& s, unsigned i, rule& r);
+unsigned read_name(const string_t& s, unsigned i, std::string& name);
+unsigned read_signed_time(const string_t& s, unsigned i, std::chrono::seconds& t);
+unsigned read_unsigned_time(const string_t& s, unsigned i, std::chrono::seconds& t);
+unsigned read_unsigned(const string_t& s, unsigned i,  unsigned limit, unsigned& u,
+                       const string_t& message = string_t{});
+
+class rule
+{
+    enum {off, J, M, N};
+
+    date::month m_;
+    date::weekday wd_;
+    unsigned short n_    : 14;
+    unsigned short mode_ : 2;
+    std::chrono::duration<std::int32_t> time_ = std::chrono::hours{2};
+
+public:
+    rule() : mode_(off) {}
+
+    bool ok() const {return mode_ != off;}
+    date::local_seconds operator()(date::year y) const;
+    std::string to_string() const;
+
+    friend std::ostream& operator<<(std::ostream& os, const rule& r);
+    friend unsigned read_date(const string_t& s, unsigned i, rule& r);
+    friend bool operator==(const rule& x, const rule& y);
+};
+
+inline
+bool
+operator==(const rule& x, const rule& y)
+{
+    if (x.mode_ != y.mode_)
+        return false;
+    switch (x.mode_)
+    {
+    case rule::J:
+    case rule::N:
+        return x.n_ == y.n_;
+    case rule::M:
+        return x.m_ == y.m_ && x.n_ == y.n_ && x.wd_ == y.wd_;
+    default:
+        return true;
+    }
+}
+
+inline
+bool
+operator!=(const rule& x, const rule& y)
+{
+    return !(x == y);
+}
+
+inline
+date::local_seconds
+rule::operator()(date::year y) const
+{
+    using date::local_days;
+    using date::January;
+    using date::days;
+    using date::last;
+    using sec = std::chrono::seconds;
+    date::local_seconds t;
+    switch (mode_)
+    {
+    case J:
+        t = local_days{y/January/0} + days{n_ + (y.is_leap() && n_ > 59)} + sec{time_};
+        break;
+    case M:
+        t = (n_ == 5 ? local_days{y/m_/wd_[last]} : local_days{y/m_/wd_[n_]}) + sec{time_};
+        break;
+    case N:
+        t = local_days{y/January/1} + days{n_} + sec{time_};
+        break;
+    default:
+        assert(!"rule called with bad mode");
+    }
+    return t;
+}
+
+inline
+std::string
+rule::to_string() const
+{
+    using namespace std::chrono;
+    auto print_offset = [](seconds off)
+        {
+            std::string nm;
+            if (off != hours{2})
+            {
+                date::hh_mm_ss<seconds> offset{off};
+                nm = '/';
+                nm += std::to_string(offset.hours().count());
+                if (offset.minutes() != minutes{0} || offset.seconds() != seconds{0})
+                {
+                    nm += ':';
+                    if (offset.minutes() < minutes{10})
+                        nm += '0';
+                    nm += std::to_string(offset.minutes().count());
+                    if (offset.seconds() != seconds{0})
+                    {
+                        nm += ':';
+                        if (offset.seconds() < seconds{10})
+                            nm += '0';
+                        nm += std::to_string(offset.seconds().count());
+                    }
+                }
+            }
+            return nm;
+        };
+
+    std::string nm;
+    switch (mode_)
+    {
+    case rule::J:
+        nm = 'J';
+        nm += std::to_string(n_);
+        break;
+    case rule::M:
+        nm = 'M';
+        nm += std::to_string(static_cast<unsigned>(m_));
+        nm += '.';
+        nm += std::to_string(n_);
+        nm += '.';
+        nm += std::to_string(wd_.c_encoding());
+        break;
+    case rule::N:
+        nm = std::to_string(n_);
+        break;
+    default:
+        break;
+    }
+    nm += print_offset(time_);
+    return nm;
+}
+
+inline
+std::ostream&
+operator<<(std::ostream& os, const rule& r)
+{
+    switch (r.mode_)
+    {
+    case rule::J:
+        os << 'J' << r.n_ << date::format(" %T", r.time_);
+        break;
+    case rule::M:
+        if (r.n_ == 5)
+            os << r.m_/r.wd_[date::last];
+        else
+            os << r.m_/r.wd_[r.n_];
+        os <<  date::format(" %T", r.time_);
+        break;
+    case rule::N:
+        os << r.n_ << date::format(" %T", r.time_);
+        break;
+    default:
+        break;
+    }
+    return os;
+}
+
+}  // namespace detail
+
+class time_zone
+{
+    std::string          std_abbrev_;
+    std::string          dst_abbrev_ = {};
+    std::chrono::seconds offset_;
+    std::chrono::seconds save_ = std::chrono::hours{1};
+    detail::rule         start_rule_;
+    detail::rule         end_rule_;
+
+public:
+    explicit time_zone(const detail::string_t& name);
+
+    template <class Duration>
+        date::sys_info   get_info(date::sys_time<Duration> st) const;
+    template <class Duration>
+        date::local_info get_info(date::local_time<Duration> tp) const;
+
+    template <class Duration>
+        date::sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_sys(date::local_time<Duration> tp) const;
+
+    template <class Duration>
+        date::sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_sys(date::local_time<Duration> tp, date::choose z) const;
+
+    template <class Duration>
+        date::local_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_local(date::sys_time<Duration> tp) const;
+
+    friend std::ostream& operator<<(std::ostream& os, const time_zone& z);
+
+    const time_zone* operator->() const {return this;}
+
+    std::string name() const;
+
+    friend bool operator==(const time_zone& x, const time_zone& y);
+
+private:
+    date::sys_seconds get_start(date::year y) const;
+    date::sys_seconds get_prev_start(date::year y) const;
+    date::sys_seconds get_next_start(date::year y) const;
+    date::sys_seconds get_end(date::year y) const;
+    date::sys_seconds get_prev_end(date::year y) const;
+    date::sys_seconds get_next_end(date::year y) const;
+    date::sys_info contant_offset() const;
+};
+
+inline
+date::sys_seconds
+time_zone::get_start(date::year y) const
+{
+    return date::sys_seconds{(start_rule_(y) - offset_).time_since_epoch()};
+}
+
+inline
+date::sys_seconds
+time_zone::get_prev_start(date::year y) const
+{
+    return date::sys_seconds{(start_rule_(--y) - offset_).time_since_epoch()};
+}
+
+inline
+date::sys_seconds
+time_zone::get_next_start(date::year y) const
+{
+    return date::sys_seconds{(start_rule_(++y) - offset_).time_since_epoch()};
+}
+
+inline
+date::sys_seconds
+time_zone::get_end(date::year y) const
+{
+    return date::sys_seconds{(end_rule_(y) - (offset_ + save_)).time_since_epoch()};
+}
+
+inline
+date::sys_seconds
+time_zone::get_prev_end(date::year y) const
+{
+    return date::sys_seconds{(end_rule_(--y) - (offset_ + save_)).time_since_epoch()};
+}
+
+inline
+date::sys_seconds
+time_zone::get_next_end(date::year y) const
+{
+    return date::sys_seconds{(end_rule_(++y) - (offset_ + save_)).time_since_epoch()};
+}
+
+inline
+date::sys_info
+time_zone::contant_offset() const
+{
+    using date::year;
+    using date::sys_info;
+    using date::sys_days;
+    using date::January;
+    using date::December;
+    using date::last;
+    using std::chrono::minutes;
+    sys_info r;
+    r.begin = sys_days{year::min()/January/1};
+    r.end   = sys_days{year::max()/December/last};
+    if (std_abbrev_.size() > 0)
+    {
+        r.abbrev = std_abbrev_;
+        r.offset = offset_;
+        r.save = {};
+    }
+    else
+    {
+        r.abbrev = dst_abbrev_;
+        r.offset = offset_ + save_;
+        r.save = date::ceil<minutes>(save_);
+    }
+    return r;
+}
+
+inline
+time_zone::time_zone(const detail::string_t& s)
+{
+    using detail::read_name;
+    using detail::read_signed_time;
+    using detail::throw_invalid;
+    auto i = read_name(s, 0, std_abbrev_);
+    auto std_name_i = i;
+    auto abbrev_name_i = i;
+    i = read_signed_time(s, i, offset_);
+    offset_ = -offset_;
+    if (i != s.size())
+    {
+        i = read_name(s, i, dst_abbrev_);
+        abbrev_name_i = i;
+        if (i != s.size())
+        {
+            if (s[i] != ',')
+            {
+                i = read_signed_time(s, i, save_);
+                save_ = -save_ - offset_;
+            }
+            if (i != s.size())
+            {
+                if (s[i] != ',')
+                    throw_invalid(s, i, "Expecting end of string or ',' to start rule");
+                ++i;
+                i = read_date(s, i, start_rule_);
+                if (i == s.size() || s[i] != ',')
+                    throw_invalid(s, i, "Expecting ',' and then the ending rule");
+                ++i;
+                i = read_date(s, i, end_rule_);
+                if (i != s.size())
+                    throw_invalid(s, i, "Found unexpected trailing characters");
+            }
+        }
+    }
+    if (start_rule_.ok())
+    {
+        if (std_abbrev_.size() < 3)
+            throw_invalid(s, std_name_i, "Zone with rules must have a std"
+                                         " abbreviation of length 3 or greater");
+        if (dst_abbrev_.size() < 3)
+            throw_invalid(s, abbrev_name_i, "Zone with rules must have a daylight"
+                                            " abbreviation of length 3 or greater");
+    }
+    else
+    {
+        if (dst_abbrev_.size() >= 3)
+        {
+            std_abbrev_.clear();
+        }
+        else if (std_abbrev_.size() < 3)
+        {
+            throw_invalid(s, std_name_i, "Zone must have at least one abbreviation"
+                                         " of length 3 or greater");
+        }
+        else
+        {
+            dst_abbrev_.clear();
+            save_ = {};
+        }
+    }
+}
+
+template <class Duration>
+date::sys_info
+time_zone::get_info(date::sys_time<Duration> st) const
+{
+    using date::sys_info;
+    using date::year_month_day;
+    using date::sys_days;
+    using date::floor;
+    using date::ceil;
+    using date::days;
+    using date::year;
+    using date::January;
+    using date::December;
+    using date::last;
+    using std::chrono::minutes;
+    sys_info r{};
+    r.offset = offset_;
+    if (start_rule_.ok())
+    {
+        auto y = year_month_day{floor<days>(st)}.year();
+        if (st >= get_next_start(y))
+            ++y;
+        else if (st < get_prev_end(y))
+            --y;
+        auto start = get_start(y);
+        auto end   = get_end(y);
+        if (start <= end)  // (northern hemisphere)
+        {
+            if (start <= st && st < end)
+            {
+                r.begin = start;
+                r.end = end;
+                r.offset += save_;
+                r.save = ceil<minutes>(save_);
+                r.abbrev = dst_abbrev_;
+            }
+            else if (st < start)
+            {
+                r.begin = get_prev_end(y);
+                r.end = start;
+                r.abbrev = std_abbrev_;
+            }
+            else  // st >= end
+            {
+                r.begin = end;
+                r.end = get_next_start(y);
+                r.abbrev = std_abbrev_;
+            }
+        }
+        else  // end < start (southern hemisphere)
+        {
+            if (end <= st && st < start)
+            {
+                r.begin = end;
+                r.end = start;
+                r.abbrev = std_abbrev_;
+            }
+            else if (st < end)
+            {
+                r.begin = get_prev_start(y);
+                r.end = end;
+                r.offset += save_;
+                r.save = ceil<minutes>(save_);
+                r.abbrev = dst_abbrev_;
+            }
+            else  // st >= start
+            {
+                r.begin = start;
+                r.end = get_next_end(y);
+                r.offset += save_;
+                r.save = ceil<minutes>(save_);
+                r.abbrev = dst_abbrev_;
+            }
+        }
+    }
+    else
+        r = contant_offset();
+    assert(r.begin <= st && st < r.end);
+    return r;
+}
+
+template <class Duration>
+date::local_info
+time_zone::get_info(date::local_time<Duration> tp) const
+{
+    using date::local_info;
+    using date::year_month_day;
+    using date::days;
+    using date::sys_days;
+    using date::sys_seconds;
+    using date::year;
+    using date::ceil;
+    using date::January;
+    using date::December;
+    using date::last;
+    using std::chrono::seconds;
+    using std::chrono::minutes;
+    local_info r{};
+    using date::floor;
+    if (start_rule_.ok())
+    {
+        auto y = year_month_day{floor<days>(tp)}.year();
+        auto start = get_start(y);
+        auto end   = get_end(y);
+        auto utcs = sys_seconds{floor<seconds>(tp - offset_).time_since_epoch()};
+        auto utcd = sys_seconds{floor<seconds>(tp - (offset_ + save_)).time_since_epoch()};
+        auto northern = start <= end;
+        if ((utcs < start) != (utcd < start))
+        {
+            if (northern)
+                r.first.begin = get_prev_end(y);
+            else
+                r.first.begin = end;
+            r.first.end = start;
+            r.first.offset = offset_;
+            r.first.abbrev = std_abbrev_;
+            r.second.begin = start;
+            if (northern)
+                r.second.end = end;
+            else
+                r.second.end = get_next_end(y);
+            r.second.abbrev = dst_abbrev_;
+            r.second.offset = offset_ + save_;
+            r.second.save = ceil<minutes>(save_);
+            r.result = save_ > seconds{0} ? local_info::nonexistent
+                                          : local_info::ambiguous;
+        }
+        else if ((utcs < end) != (utcd < end))
+        {
+            if (northern)
+                r.first.begin = start;
+            else
+                r.first.begin = get_prev_start(y);
+            r.first.end = end;
+            r.first.offset = offset_ + save_;
+            r.first.save = ceil<minutes>(save_);
+            r.first.abbrev = dst_abbrev_;
+            r.second.begin = end;
+            if (northern)
+                r.second.end = get_next_start(y);
+            else
+                r.second.end = start;
+            r.second.abbrev = std_abbrev_;
+            r.second.offset = offset_;
+            r.result = save_ > seconds{0} ? local_info::ambiguous
+                                          : local_info::nonexistent;
+        }
+        else
+            r.first = get_info(utcs);
+    }
+    else
+        r.first = contant_offset();
+    return r;
+}
+
+template <class Duration>
+date::sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_sys(date::local_time<Duration> tp) const
+{
+    using date::local_info;
+    using date::sys_time;
+    using date::ambiguous_local_time;
+    using date::nonexistent_local_time;
+    auto i = get_info(tp);
+    if (i.result == local_info::nonexistent)
+        throw nonexistent_local_time(tp, i);
+    else if (i.result == local_info::ambiguous)
+        throw ambiguous_local_time(tp, i);
+    return sys_time<Duration>{tp.time_since_epoch()} - i.first.offset;
+}
+
+template <class Duration>
+date::sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_sys(date::local_time<Duration> tp, date::choose z) const
+{
+    using date::local_info;
+    using date::sys_time;
+    using date::choose;
+    auto i = get_info(tp);
+    if (i.result == local_info::nonexistent)
+    {
+        return i.first.end;
+    }
+    else if (i.result == local_info::ambiguous)
+    {
+        if (z == choose::latest)
+            return sys_time<Duration>{tp.time_since_epoch()} - i.second.offset;
+    }
+    return sys_time<Duration>{tp.time_since_epoch()} - i.first.offset;
+}
+
+template <class Duration>
+date::local_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_local(date::sys_time<Duration> tp) const
+{
+    using date::local_time;
+    using std::chrono::seconds;
+    using LT = local_time<typename std::common_type<Duration, seconds>::type>;
+    auto i = get_info(tp);
+    return LT{(tp + i.offset).time_since_epoch()};
+}
+
+inline
+std::ostream&
+operator<<(std::ostream& os, const time_zone& z)
+{
+    using date::operator<<;
+    os << '{';
+    os << z.std_abbrev_ << ", " << z.dst_abbrev_ << date::format(", %T, ", z.offset_)
+       << date::format("%T, [", z.save_) << z.start_rule_ << ", " << z.end_rule_ << ")}";
+    return os;
+}
+
+inline
+std::string
+time_zone::name() const
+{
+    using namespace date;
+    using namespace std::chrono;
+    auto print_abbrev = [](std::string const& nm)
+        {
+            if (std::any_of(nm.begin(), nm.end(),
+                         [](char c)
+                         {
+                             return !std::isalpha(c);
+                         }))
+            {
+                return '<' + nm + '>';
+            }
+            return nm;
+        };
+    auto print_offset = [](seconds off)
+        {
+            std::string nm;
+            hh_mm_ss<seconds> offset{-off};
+            if (offset.is_negative())
+                nm += '-';
+            nm += std::to_string(offset.hours().count());
+            if (offset.minutes() != minutes{0} || offset.seconds() != seconds{0})
+            {
+                nm += ':';
+                if (offset.minutes() < minutes{10})
+                    nm += '0';
+                nm += std::to_string(offset.minutes().count());
+                if (offset.seconds() != seconds{0})
+                {
+                    nm += ':';
+                    if (offset.seconds() < seconds{10})
+                        nm += '0';
+                    nm += std::to_string(offset.seconds().count());
+                }
+            }
+            return nm;
+        };
+    auto nm = print_abbrev(std_abbrev_);
+    nm += print_offset(offset_);
+    if (!dst_abbrev_.empty())
+    {
+        nm += print_abbrev(dst_abbrev_);
+        if (save_ != hours{1})
+            nm += print_offset(offset_+save_);
+        if (start_rule_.ok())
+        {
+            nm += ',';
+            nm += start_rule_.to_string();
+            nm += ',';
+            nm += end_rule_.to_string();
+        }
+    }
+    return nm;
+}
+
+inline
+bool
+operator==(const time_zone& x, const time_zone& y)
+{
+    return x.std_abbrev_ == y.std_abbrev_ &&
+           x.dst_abbrev_ == y. dst_abbrev_ &&
+           x.offset_ == y.offset_ &&
+           x.save_ == y.save_ &&
+           x.start_rule_ == y.start_rule_ &&
+           x.end_rule_ == y.end_rule_;
+}
+
+inline
+bool
+operator!=(const time_zone& x, const time_zone& y)
+{
+    return !(x == y);
+}
+
+namespace detail
+{
+
+inline
+void
+throw_invalid(const string_t& s, unsigned i, const string_t& message)
+{
+    throw std::runtime_error(std::string("Invalid time_zone initializer.\n") +
+                             std::string(message) + ":\n" +
+                             std::string(s) + '\n' +
+                             "\x1b[1;32m" +
+                             std::string(i, '~') + '^' +
+                             std::string(i < s.size() ? s.size()-i-1 : 0, '~') +
+                             "\x1b[0m");
+}
+
+inline
+unsigned
+read_date(const string_t& s, unsigned i, rule& r)
+{
+    using date::month;
+    using date::weekday;
+    if (i == s.size())
+        throw_invalid(s, i, "Expected rule but found end of string");
+    if (s[i] == 'J')
+    {
+        ++i;
+        unsigned n;
+        i = read_unsigned(s, i, 3, n, "Expected to find the Julian day [1, 365]");
+        if (!(1 <= n && n <= 365))
+            throw_invalid(s, i-1, "Expected Julian day to be in the range [1, 365]");
+        r.mode_ = rule::J;
+        r.n_ = n;
+    }
+    else if (s[i] == 'M')
+    {
+        ++i;
+        unsigned m;
+        i = read_unsigned(s, i, 2, m, "Expected to find month [1, 12]");
+        if (!(1 <= m && m <= 12))
+            throw_invalid(s, i-1, "Expected month to be in the range [1, 12]");
+        if (i == s.size() || s[i] != '.')
+            throw_invalid(s, i, "Expected '.' after month");
+        ++i;
+        unsigned n;
+        i = read_unsigned(s, i, 1, n, "Expected to find week number [1, 5]");
+        if (!(1 <= n && n <= 5))
+            throw_invalid(s, i-1, "Expected week number to be in the range [1, 5]");
+        if (i == s.size() || s[i] != '.')
+            throw_invalid(s, i, "Expected '.' after weekday index");
+        ++i;
+        unsigned wd;
+        i = read_unsigned(s, i, 1, wd, "Expected to find day of week [0, 6]");
+        if (wd > 6)
+            throw_invalid(s, i-1, "Expected day of week to be in the range [0, 6]");
+        r.mode_ = rule::M;
+        r.m_ = month{m};
+        r.wd_ = weekday{wd};
+        r.n_ = n;
+    }
+    else if (std::isdigit(s[i]))
+    {
+        unsigned n;
+        i = read_unsigned(s, i, 3, n);
+        if (n > 365)
+            throw_invalid(s, i-1, "Expected Julian day to be in the range [0, 365]");
+        r.mode_ = rule::N;
+        r.n_ = n;
+    }
+    else
+        throw_invalid(s, i, "Expected 'J', 'M', or a digit to start rule");
+    if (i != s.size() && s[i] == '/')
+    {
+        ++i;
+        std::chrono::seconds t;
+        i = read_unsigned_time(s, i, t);
+        r.time_ = t;
+    }
+    return i;
+}
+
+inline
+unsigned
+read_name(const string_t& s, unsigned i, std::string& name)
+{
+    if (i == s.size())
+        throw_invalid(s, i, "Expected a name but found end of string");
+    if (s[i] == '<')
+    {
+        ++i;
+        while (true)
+        {
+            if (i == s.size())
+                throw_invalid(s, i,
+                              "Expected to find closing '>', but found end of string");
+            if (s[i] == '>')
+                break;
+            name.push_back(s[i]);
+            ++i;
+        }
+        ++i;
+    }
+    else
+    {
+        while (i != s.size() && std::isalpha(s[i]))
+        {
+            name.push_back(s[i]);
+            ++i;
+        }
+    }
+    return i;
+}
+
+inline
+unsigned
+read_signed_time(const string_t& s, unsigned i,
+                                  std::chrono::seconds& t)
+{
+    if (i == s.size())
+        throw_invalid(s, i, "Expected to read signed time, but found end of string");
+    bool negative = false;
+    if (s[i] == '-')
+    {
+        negative = true;
+        ++i;
+    }
+    else if (s[i] == '+')
+        ++i;
+    i = read_unsigned_time(s, i, t);
+    if (negative)
+        t = -t;
+    return i;
+}
+
+inline
+unsigned
+read_unsigned_time(const string_t& s, unsigned i, std::chrono::seconds& t)
+{
+    using std::chrono::seconds;
+    using std::chrono::minutes;
+    using std::chrono::hours;
+    if (i == s.size())
+        throw_invalid(s, i, "Expected to read unsigned time, but found end of string");
+    unsigned x;
+    i = read_unsigned(s, i, 2, x, "Expected to find hours [0, 24]");
+    if (x > 24)
+        throw_invalid(s, i-1, "Expected hours to be in the range [0, 24]");
+    t = hours{x};
+    if (i != s.size() && s[i] == ':')
+    {
+        ++i;
+        i = read_unsigned(s, i, 2, x, "Expected to find minutes [0, 59]");
+        if (x > 59)
+            throw_invalid(s, i-1, "Expected minutes to be in the range [0, 59]");
+        t += minutes{x};
+        if (i != s.size() && s[i] == ':')
+        {
+            ++i;
+            i = read_unsigned(s, i, 2, x, "Expected to find seconds [0, 59]");
+            if (x > 59)
+                throw_invalid(s, i-1, "Expected seconds to be in the range [0, 59]");
+            t += seconds{x};
+        }
+    }
+    return i;
+}
+
+inline
+unsigned
+read_unsigned(const string_t& s, unsigned i, unsigned limit, unsigned& u,
+              const string_t& message)
+{
+    if (i == s.size() || !std::isdigit(s[i]))
+        throw_invalid(s, i, message);
+    u = static_cast<unsigned>(s[i] - '0');
+    unsigned count = 1;
+    for (++i; count < limit && i != s.size() && std::isdigit(s[i]); ++i, ++count)
+        u = u * 10 + static_cast<unsigned>(s[i] - '0');
+    return i;
+}
+
+}  // namespace detail
+
+}  // namespace Posix
+
+namespace date
+{
+
+template <>
+struct zoned_traits<Posix::time_zone>
+{
+
+#if HAS_STRING_VIEW
+
+    static
+    Posix::time_zone
+    locate_zone(std::string_view name)
+    {
+        return Posix::time_zone{name};
+    }
+
+#else  // !HAS_STRING_VIEW
+
+    static
+    Posix::time_zone
+    locate_zone(const std::string& name)
+    {
+        return Posix::time_zone{name};
+    }
+
+    static
+    Posix::time_zone
+    locate_zone(const char* name)
+    {
+        return Posix::time_zone{name};
+    }
+
+#endif  // !HAS_STRING_VIEW
+
+};
+
+}  // namespace date
+
+#endif  // PTZ_H

src/date/tz_private.h

@@ -0,0 +1,316 @@
+#ifndef TZ_PRIVATE_H
+#define TZ_PRIVATE_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2015, 2016 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// Our apologies.  When the previous paragraph was written, lowercase had not yet
+// been invented (that would involve another several millennia of evolution).
+// We did not mean to shout.
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+#include "tz.h"
+#else
+#include "date.h"
+#include <vector>
+#endif
+
+namespace date
+{
+
+namespace detail
+{
+
+#if !USE_OS_TZDB
+
+enum class tz {utc, local, standard};
+
+//forward declare to avoid warnings in gcc 6.2
+class MonthDayTime;
+std::istream& operator>>(std::istream& is, MonthDayTime& x);
+std::ostream& operator<<(std::ostream& os, const MonthDayTime& x);
+
+
+class MonthDayTime
+{
+private:
+    struct pair
+    {
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+        pair() : month_day_(date::jan / 1), weekday_(0U) {}
+
+        pair(const date::month_day& month_day, const date::weekday& weekday)
+            : month_day_(month_day), weekday_(weekday) {}
+#endif
+
+        date::month_day month_day_;
+        date::weekday   weekday_;
+    };
+
+    enum Type {month_day, month_last_dow, lteq, gteq};
+
+    Type                         type_{month_day};
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+    union U
+#else
+    struct U
+#endif
+    {
+        date::month_day          month_day_;
+        date::month_weekday_last month_weekday_last_;
+        pair                     month_day_weekday_;
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+        U() : month_day_{date::jan/1} {}
+#else
+        U() :
+            month_day_(date::jan/1),
+            month_weekday_last_(date::month(0U), date::weekday_last(date::weekday(0U)))
+        {}
+
+#endif // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+        U& operator=(const date::month_day& x);
+        U& operator=(const date::month_weekday_last& x);
+        U& operator=(const pair& x);
+    } u;
+
+    std::chrono::hours           h_{0};
+    std::chrono::minutes         m_{0};
+    std::chrono::seconds         s_{0};
+    tz                           zone_{tz::local};
+
+public:
+    MonthDayTime() = default;
+    MonthDayTime(local_seconds tp, tz timezone);
+    MonthDayTime(const date::month_day& md, tz timezone);
+
+    date::day day() const;
+    date::month month() const;
+    tz zone() const {return zone_;}
+
+    void canonicalize(date::year y);
+
+    sys_seconds
+       to_sys(date::year y, std::chrono::seconds offset, std::chrono::seconds save) const;
+    sys_days to_sys_days(date::year y) const;
+
+    sys_seconds to_time_point(date::year y) const;
+    int compare(date::year y, const MonthDayTime& x, date::year yx,
+                std::chrono::seconds offset, std::chrono::minutes prev_save) const;
+
+    friend std::istream& operator>>(std::istream& is, MonthDayTime& x);
+    friend std::ostream& operator<<(std::ostream& os, const MonthDayTime& x);
+};
+
+// A Rule specifies one or more set of datetimes without using an offset.
+// Multiple dates are specified with multiple years.  The years in effect
+// go from starting_year_ to ending_year_, inclusive.  starting_year_ <=
+// ending_year_. save_ is in effect for times from the specified time
+// onward, including the specified time. When the specified time is
+// local, it uses the save_ from the chronologically previous Rule, or if
+// there is none, 0.
+
+//forward declare to avoid warnings in gcc 6.2
+class Rule;
+bool operator==(const Rule& x, const Rule& y);
+bool operator<(const Rule& x, const Rule& y);
+bool operator==(const Rule& x, const date::year& y);
+bool operator<(const Rule& x, const date::year& y);
+bool operator==(const date::year& x, const Rule& y);
+bool operator<(const date::year& x, const Rule& y);
+bool operator==(const Rule& x, const std::string& y);
+bool operator<(const Rule& x, const std::string& y);
+bool operator==(const std::string& x, const Rule& y);
+bool operator<(const std::string& x, const Rule& y);
+std::ostream& operator<<(std::ostream& os, const Rule& r);
+
+class Rule
+{
+private:
+    std::string          name_;
+    date::year           starting_year_{0};
+    date::year           ending_year_{0};
+    MonthDayTime         starting_at_;
+    std::chrono::minutes save_{0};
+    std::string          abbrev_;
+
+public:
+    Rule() = default;
+    explicit Rule(const std::string& s);
+    Rule(const Rule& r, date::year starting_year, date::year ending_year);
+
+    const std::string& name() const {return name_;}
+    const std::string& abbrev() const {return abbrev_;}
+
+    const MonthDayTime&         mdt()           const {return starting_at_;}
+    const date::year&           starting_year() const {return starting_year_;}
+    const date::year&           ending_year()   const {return ending_year_;}
+    const std::chrono::minutes& save()          const {return save_;}
+
+    static void split_overlaps(std::vector<Rule>& rules);
+
+    friend bool operator==(const Rule& x, const Rule& y);
+    friend bool operator<(const Rule& x, const Rule& y);
+    friend bool operator==(const Rule& x, const date::year& y);
+    friend bool operator<(const Rule& x, const date::year& y);
+    friend bool operator==(const date::year& x, const Rule& y);
+    friend bool operator<(const date::year& x, const Rule& y);
+    friend bool operator==(const Rule& x, const std::string& y);
+    friend bool operator<(const Rule& x, const std::string& y);
+    friend bool operator==(const std::string& x, const Rule& y);
+    friend bool operator<(const std::string& x, const Rule& y);
+
+    friend std::ostream& operator<<(std::ostream& os, const Rule& r);
+
+private:
+    date::day day() const;
+    date::month month() const;
+    static void split_overlaps(std::vector<Rule>& rules, std::size_t i, std::size_t& e);
+    static bool overlaps(const Rule& x, const Rule& y);
+    static void split(std::vector<Rule>& rules, std::size_t i, std::size_t k,
+                      std::size_t& e);
+};
+
+inline bool operator!=(const Rule& x, const Rule& y) {return !(x == y);}
+inline bool operator> (const Rule& x, const Rule& y) {return   y < x;}
+inline bool operator<=(const Rule& x, const Rule& y) {return !(y < x);}
+inline bool operator>=(const Rule& x, const Rule& y) {return !(x < y);}
+
+inline bool operator!=(const Rule& x, const date::year& y) {return !(x == y);}
+inline bool operator> (const Rule& x, const date::year& y) {return   y < x;}
+inline bool operator<=(const Rule& x, const date::year& y) {return !(y < x);}
+inline bool operator>=(const Rule& x, const date::year& y) {return !(x < y);}
+
+inline bool operator!=(const date::year& x, const Rule& y) {return !(x == y);}
+inline bool operator> (const date::year& x, const Rule& y) {return   y < x;}
+inline bool operator<=(const date::year& x, const Rule& y) {return !(y < x);}
+inline bool operator>=(const date::year& x, const Rule& y) {return !(x < y);}
+
+inline bool operator!=(const Rule& x, const std::string& y) {return !(x == y);}
+inline bool operator> (const Rule& x, const std::string& y) {return   y < x;}
+inline bool operator<=(const Rule& x, const std::string& y) {return !(y < x);}
+inline bool operator>=(const Rule& x, const std::string& y) {return !(x < y);}
+
+inline bool operator!=(const std::string& x, const Rule& y) {return !(x == y);}
+inline bool operator> (const std::string& x, const Rule& y) {return   y < x;}
+inline bool operator<=(const std::string& x, const Rule& y) {return !(y < x);}
+inline bool operator>=(const std::string& x, const Rule& y) {return !(x < y);}
+
+struct zonelet
+{
+    enum tag {has_rule, has_save, is_empty};
+
+    std::chrono::seconds gmtoff_;
+    tag tag_ = has_rule;
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+    union U
+#else
+    struct U
+#endif
+    {
+        std::string          rule_;
+        std::chrono::minutes save_;
+
+        ~U() {}
+        U() {}
+        U(const U&) {}
+        U& operator=(const U&) = delete;
+    } u;
+
+    std::string                        format_;
+    date::year                         until_year_{0};
+    MonthDayTime                       until_date_;
+    sys_seconds                        until_utc_;
+    local_seconds                      until_std_;
+    local_seconds                      until_loc_;
+    std::chrono::minutes               initial_save_{0};
+    std::string                        initial_abbrev_;
+    std::pair<const Rule*, date::year> first_rule_{nullptr, date::year::min()};
+    std::pair<const Rule*, date::year> last_rule_{nullptr, date::year::max()};
+
+    ~zonelet();
+    zonelet();
+    zonelet(const zonelet& i);
+    zonelet& operator=(const zonelet&) = delete;
+};
+
+#else  // USE_OS_TZDB
+
+struct ttinfo
+{
+    std::int32_t  tt_gmtoff;
+    unsigned char tt_isdst;
+    unsigned char tt_abbrind;
+    unsigned char pad[2];
+};
+
+static_assert(sizeof(ttinfo) == 8, "");
+
+struct expanded_ttinfo
+{
+    std::chrono::seconds offset;
+    std::string          abbrev;
+    bool                 is_dst;
+};
+
+struct transition
+{
+    sys_seconds            timepoint;
+    const expanded_ttinfo* info;
+
+    transition(sys_seconds tp, const expanded_ttinfo* i = nullptr)
+        : timepoint(tp)
+        , info(i)
+        {}
+
+    friend
+    std::ostream&
+    operator<<(std::ostream& os, const transition& t)
+    {
+        using date::operator<<;
+        os << t.timepoint << "Z ";
+        if (t.info->offset >= std::chrono::seconds{0})
+            os << '+';
+        os << make_time(t.info->offset);
+        if (t.info->is_dst > 0)
+            os << " daylight ";
+        else
+            os << " standard ";
+        os << t.info->abbrev;
+        return os;
+    }
+};
+
+#endif  // USE_OS_TZDB
+
+}  // namespace detail
+
+}  // namespace date
+
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#include "tz.h"
+#endif
+
+#endif  // TZ_PRIVATE_H