tests: check more timezones

Author: henryiii

include/pybind11/chrono.h

@@ -150,30 +150,21 @@ 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)
-        auto us = duration_cast<us_t>(src.time_since_epoch() % seconds(1));
-        if (us.count() < 0)
-            us += seconds(1);
-
-        // Subtract microseconds BEFORE `system_clock::to_time_t`, because:
-        // > If std::time_t has lower precision, it is implementation-defined whether the value is rounded or truncated.
-        // (https://en.cppreference.com/w/cpp/chrono/system_clock/to_time_t)
-        std::time_t tt = system_clock::to_time_t(time_point_cast<system_clock::duration>(src - us));
+        std::time_t tt = system_clock::to_time_t(time_point_cast<system_clock::duration>(src));
         // this function uses static memory so it's best to copy it out asap just in case
         // otherwise other code that is using localtime may break this (not just python code)
         std::tm localtime = *std::localtime(&tt);
 
+        // Declare these special duration types so the conversions happen with the correct primitive types (int)
+        using us_t = duration<int, std::micro>;
+
         return PyDateTime_FromDateAndTime(localtime.tm_year + 1900,
                                           localtime.tm_mon + 1,
                                           localtime.tm_mday,
                                           localtime.tm_hour,
                                           localtime.tm_min,
                                           localtime.tm_sec,
-                                          us.count());
+                                          (duration_cast<us_t>(src.time_since_epoch() % seconds(1))).count());
     }
     PYBIND11_TYPE_CASTER(type, _("datetime.datetime"));
 };

tests/test_chrono.py

@@ -81,7 +81,14 @@ def test_chrono_system_clock_roundtrip_date():
     datetime.time(5, 59, 59, 0),
     datetime.time(5, 59, 59, 1),
 ])
-def test_chrono_system_clock_roundtrip_time(time1):
+@pytest.mark.parametrize("tz", [
+    "/usr/share/zoneinfo/Europe/Brussels",
+    "/usr/share/zoneinfo/Asia/Pyongyang",
+    "/usr/share/zoneinfo/America/New_York",
+])
+def test_chrono_system_clock_roundtrip_time(time1, tz, monkeypatch):
+    monkeypatch.setenv("TZ", tz)
+
     # Roundtrip the time
     datetime2 = m.test_chrono2(time1)
     date2 = datetime2.date()