Implement locale-specific minute formatting

include/fmt/time.h

@@ -206,9 +206,13 @@ struct chrono_formatter {
     format_localized(time, 'I');
   }
 
-  void on_minute(numeric_system) {
+  void on_minute(numeric_system ns) {
     auto minute = to_int((s.count() / 60) % 60);
-    write(minute, 2);
+    if (ns == numeric_system::standard)
+      return write(minute, 2);
+    auto time = tm();
+    time.tm_minute = minute;
+    format_localized(time, 'M');
   }
 
   void on_second(numeric_system) {

test/time-test.cc

@@ -107,5 +107,8 @@ TEST(TimeTest, ChronoLocale) {
   EXPECT_EQ(str(), fmt::format(loc, "{:%OH}", std::chrono::hours(14)));
   os << std::put_time(&time, "%OI");
   EXPECT_EQ(str(), fmt::format(loc, "{:%OI}", std::chrono::hours(14)));
+  time.tm_minute = 42;
+  os << std::put_time(&time, "%OM");
+  EXPECT_EQ(str(), fmt::format(loc, "{:%OM}", std::chrono::minutes(42)));
 }
 #endif