From cb4bf26fc7e80a1285d4a704990988e6c2d44103 Mon Sep 17 00:00:00 2001
From: maximilianriemensberger
 <maximilianriemensberger@users.noreply.github.com>
Date: Tue, 13 Aug 2019 09:57:42 +0200
Subject: [PATCH] Fix compilation error with GCC 5

GCC 5 complains that `operator-=` and `operator+=` are not constexpr.  The `-` and `+` operator appear seem to be fine.
---
 include/date/date.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/date/date.h b/include/date/date.h
index be68a87..90bdcf5 100644
--- a/include/date/date.h
+++ b/include/date/date.h
@@ -3917,7 +3917,7 @@ make12(std::chrono::hours h) NOEXCEPT
     else
     {
         if (h != hours{12})
-            h -= hours{12};
+            h = h - hours{12};
     }
     return h;
 }
@@ -3931,7 +3931,7 @@ make24(std::chrono::hours h, bool is_pm) NOEXCEPT
     if (is_pm)
     {
         if (h != hours{12})
-            h += hours{12};
+            h = h + hours{12};
     }
     else if (h == hours{12})
         h = hours{0};