34   ym0 += months{50};  in constexpr_year_month()
35   ym0 -= months{50};  in constexpr_year_month()
61   static_assert(ym1 + months{6} == 2015y/December);  in constexpr_year_month()
62   static_assert(ym1 + months{7} == 2016y/January);  in constexpr_year_month()
63   static_assert(months{24} + ym1 == 2017y/June);  in constexpr_year_month()
64   static_assert(months{25} + ym1 == 2017y/July);  in constexpr_year_month()
66   static_assert(ym1 + months{-5} == 2015y/January);  in constexpr_year_month()
67   static_assert(ym1 + months{-6} == 2014y/December);  in constexpr_year_month()
68   static_assert(ym1 + months{-24} == 2013y/June);  in constexpr_year_month()
69   static_assert(ym1 + months{-25} == 2013y/May);  in constexpr_year_month()
71   static_assert(ym1 - months{5} == 2015y/January);  in constexpr_year_month()
72   static_assert(ym1 - months{6} == 2014y/December);  in constexpr_year_month()
73   static_assert(ym1 - months{24} == 2013y/June);  in constexpr_year_month()
74   static_assert(ym1 - months{25} == 2013y/May);  in constexpr_year_month()
76   static_assert(ym2 - ym1 == months{11});  in constexpr_year_month()
77   static_assert(ym1 - ym2 == -months{11});  in constexpr_year_month()
83   static_assert(2017y/33 + months{0} == 2019y/9);  in constexpr_year_month()
85   static_assert(2010y/January + months{-12} == 2009y/January);  in constexpr_year_month()
87   static_assert(2010y/month{0} + months{-1} == 2009y/November);  in constexpr_year_month()
88   static_assert(2010y/month{0} + months{0} == 2009y/December);  in constexpr_year_month()
89   static_assert(2010y/month{0} + months{1} == 2010y/January);  in constexpr_year_month()
90   static_assert(2010y/month{0} + months{2} == 2010y/February);  in constexpr_year_month()
91   static_assert(2010y/month{0} + months{11} == 2010y/November);  in constexpr_year_month()
92   static_assert(2010y/month{0} + months{12} == 2010y/December);  in constexpr_year_month()
93   static_assert(2010y/month{0} + months{13} == 2011y/January);  in constexpr_year_month()
95   static_assert(months{-1} + 2010y/month{37} == 2012y/December);  in constexpr_year_month()
96   static_assert(months{0} + 2010y/month{37} == 2013y/January);  in constexpr_year_month()
97   static_assert(months{1} + 2010y/month{37} == 2013y/February);  in constexpr_year_month()