From 7816c3b48f343acba22608dd2046e4ceec5de6e7 Mon Sep 17 00:00:00 2001
From: Howard Hinnant <howard.hinnant@gmail.com>
Date: Sun, 28 Aug 2016 14:26:22 -0400
Subject: [PATCH] Eliminate dependence on OS's timegm / _mkgmtime

Apple's OS timegm has a 32 bit bug meaning it can't parse dates earlier
than 1901-12-13 20:45:52.
---
 date.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/date.h b/date.h
index 8017db0..cf28bd5 100644
--- a/date.h
+++ b/date.h
@@ -4286,12 +4286,12 @@ parse(std::basic_istream<CharT, Traits>& is,
                 f.get(is, 0, is, err, &tm, b, e);
             if ((err & ios_base::failbit) == 0)
             {
-#ifdef _WIN32
-                auto tt = _mkgmtime(&tm);
-#else
-                auto tt = timegm(&tm);
-#endif
-                tp = floor<Duration>(system_clock::from_time_t(tt) + subseconds);
+                using namespace std::chrono;
+                tp = floor<Duration>(sys_days{year{tm.tm_year + 1900}/
+                                             (tm.tm_mon+1)/
+                                             (tm.tm_mday)} +
+                                     hours{tm.tm_hour} +  minutes{tm.tm_min} +
+                                     seconds{tm.tm_sec} + subseconds);
                 abbrev = std::move(temp_abbrev);
                 offset = temp_offset;
             }