Improve Windows compatibility of Clock implementation

Author: robsdedude

neo4j/time/__init__.py

@@ -266,7 +266,10 @@ def local_offset(cls):
 
         :raises OverflowError:
         """
-        return ClockTime(-int(mktime(gmtime(0))))
+        # Adding and subtracting two days to avoid passing a pre-epoch time to
+        # `mktime`, which can cause a `OverflowError` on some platforms (e.g.,
+        # Windows).
+        return ClockTime(-int(mktime(gmtime(172800))) + 172800)
 
     def local_time(self):
         """ Read and return the current local time from this clock, measured relative to the Unix Epoch.

tests/unit/time/test_clock.py

@@ -53,3 +53,19 @@ def test_local_offset(self):
         clock = object.__new__(Clock)
         offset = clock.local_offset()
         self.assertIsInstance(offset, ClockTime)
+
+    def test_local_time(self):
+        _ = Clock()
+        for impl in Clock._Clock__implementations:
+            self.assert_(issubclass(impl, Clock))
+            clock = object.__new__(impl)
+            time = clock.local_time()
+            self.assertIsInstance(time, ClockTime)
+
+    def test_utc_time(self):
+        _ = Clock()
+        for impl in Clock._Clock__implementations:
+            self.assert_(issubclass(impl, Clock))
+            clock = object.__new__(impl)
+            time = clock.utc_time()
+            self.assertIsInstance(time, ClockTime)