Test tm timezone formatting

Author: vitaut

test/chrono-test.cc

@@ -339,6 +339,12 @@ TEST(chrono_test, local_time) {
 TEST(chrono_test, tm) {
   auto time = fmt::gmtime(290088000);
   test_time(time);
+  if (fmt::detail::has_member_data_tm_gmtoff<std::tm>()) {
+    EXPECT_EQ(fmt::format(fmt::runtime("{:%z}"), time), "+0000");
+    EXPECT_EQ(fmt::format(fmt::runtime("{:%Ez}"), time), "+00:00");
+    EXPECT_EQ(fmt::format(fmt::runtime("{:%Oz}"), time), "+00:00");
+    EXPECT_EQ(fmt::format(fmt::runtime("{:%Z}"), time), "UTC");
+  }
 }
 
 TEST(chrono_test, daylight_savings_time_end) {