[time.cal.day.nonmembers] 'onstexpr' -> 'constexpr'

Author: zygoloid

source/time.tex

@@ -3882,7 +3882,7 @@
 
 \indexlibrarymember{operator<=>}{day}%
 \begin{itemdecl}
-onstexpr strong_ordering operator<=>(const day& x, const day& y) noexcept;
+constexpr strong_ordering operator<=>(const day& x, const day& y) noexcept;
 \end{itemdecl}
 
 \begin{itemdescr}