From c99a40b8469996a7963c85ea0ef5b6d329ce2e89 Mon Sep 17 00:00:00 2001
From: Howard Hinnant <howard.hinnant@gmail.com>
Date: Sat, 1 Aug 2015 19:16:33 -0400
Subject: [PATCH] Add year_month += and -= operators.

---
 date.h | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/date.h b/date.h
index 6b771f2..f7bd09e 100644
--- a/date.h
+++ b/date.h
@@ -382,6 +382,11 @@ public:
     CONSTCD11 date::year  year()  const noexcept;
     CONSTCD11 date::month month() const noexcept;
 
+    year_month& operator+=(const months& dm) noexcept;
+    year_month& operator-=(const months& dm) noexcept;
+    year_month& operator+=(const years& dy) noexcept;
+    year_month& operator-=(const years& dy) noexcept;
+
     CONSTCD11 bool ok() const noexcept;
 };
 
@@ -1537,6 +1542,38 @@ CONSTCD11 inline year year_month::year() const noexcept {return y_;}
 CONSTCD11 inline month year_month::month() const noexcept {return m_;}
 CONSTCD11 inline bool year_month::ok() const noexcept {return y_.ok() && m_.ok();}
 
+inline
+year_month&
+year_month::operator+=(const months& dm) noexcept
+{
+    *this = *this + dm;
+    return *this;
+}
+
+inline
+year_month&
+year_month::operator-=(const months& dm) noexcept
+{
+    *this = *this - dm;
+    return *this;
+}
+
+inline
+year_month&
+year_month::operator+=(const years& dy) noexcept
+{
+    *this = *this + dy;
+    return *this;
+}
+
+inline
+year_month&
+year_month::operator-=(const years& dy) noexcept
+{
+    *this = *this - dy;
+    return *this;
+}
+
 CONSTCD11
 inline
 bool