Fix review remarks: remove useless comment and skip setting TZ enviro…

…nment variable on Windows

include/pybind11/chrono.h

@@ -150,11 +150,9 @@ template <typename Duration> class type_caster<std::chrono::time_point<std::chro
         // Lazy initialise the PyDateTime import
         if (!PyDateTimeAPI) { PyDateTime_IMPORT; }
 
-        // Declare these special duration types so the conversions happen with the correct primitive types (int)
-        using us_t = duration<int, std::micro>;
-
         // Get out microseconds, and make sure they are positive, to avoid bug in eastern hemisphere time zones
         // (cfr. https://github.com/pybind/pybind11/issues/2417)
+        using us_t = duration<int, std::micro>;
         auto us = duration_cast<us_t>(src.time_since_epoch() % seconds(1));
         if (us.count() < 0)
             us += seconds(1);

tests/test_chrono.py

@@ -71,6 +71,11 @@ def test_chrono_system_clock_roundtrip_date():
     assert time2.microsecond == 0
 
 
+SKIP_TZ_ENV_ON_WIN = pytest.mark.skipif(
+    "env.WIN", reason="TZ environment variable only supported on POSIX"
+)
+
+
 @pytest.mark.parametrize("time1", [
     datetime.datetime.today().time(),
     datetime.time(0, 0, 0),
@@ -82,12 +87,14 @@ def test_chrono_system_clock_roundtrip_date():
     datetime.time(5, 59, 59, 1),
 ])
 @pytest.mark.parametrize("tz", [
-    "Europe/Brussels",
-    "Asia/Pyongyang",
-    "America/New_York",
+    None,
+    pytest.param("Europe/Brussels", marks=SKIP_TZ_ENV_ON_WIN),
+    pytest.param("Asia/Pyongyang", marks=SKIP_TZ_ENV_ON_WIN),
+    pytest.param("America/New_York", marks=SKIP_TZ_ENV_ON_WIN),
 ])
 def test_chrono_system_clock_roundtrip_time(time1, tz, monkeypatch):
-    monkeypatch.setenv("TZ", "/usr/share/zoneinfo/{}".format(tz))
+    if tz is not None:
+        monkeypatch.setenv("TZ", "/usr/share/zoneinfo/{}".format(tz))
 
     # Roundtrip the time
     datetime2 = m.test_chrono2(time1)