Fix MAX_TIMESTAMP calculation to use UTC timezone

arrow/constants.py

@@ -1,7 +1,7 @@
 """Constants used internally in arrow."""
 
 import sys
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Final
 
 # datetime.max.timestamp() errors on Windows, so we must hardcode
@@ -11,17 +11,17 @@
 try:
     # Get max timestamp. Works on POSIX-based systems like Linux and macOS,
     # but will trigger an OverflowError, ValueError, or OSError on Windows
-    _MAX_TIMESTAMP = datetime.max.timestamp()
+    _MAX_TIMESTAMP = datetime.max.replace(tzinfo=timezone.utc).timestamp()
 except (OverflowError, ValueError, OSError):  # pragma: no cover
     # Fallback for Windows and 32-bit systems if initial max timestamp call fails
     # Must get max value of ctime on Windows based on architecture (x32 vs x64)
     # https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/ctime-ctime32-ctime64-wctime-wctime32-wctime64
     # Note: this may occur on both 32-bit Linux systems (issue #930) along with Windows systems
     is_64bits = sys.maxsize > 2**32
     _MAX_TIMESTAMP = (
-        datetime(3000, 1, 1, 23, 59, 59, 999999).timestamp()
+        datetime(3000, 1, 1, 23, 59, 59, 999999, tzinfo=timezone.utc).timestamp()
         if is_64bits
-        else datetime(2038, 1, 1, 23, 59, 59, 999999).timestamp()
+        else datetime(2038, 1, 1, 23, 59, 59, 999999, tzinfo=timezone.utc).timestamp()
     )
 
 MAX_TIMESTAMP: Final[float] = _MAX_TIMESTAMP

tests/test_arrow.py

@@ -3097,3 +3097,17 @@ def test_get_iteration_params(self):
 
         with pytest.raises(ValueError):
             arrow.Arrow._get_iteration_params(None, None)
+
+
+class TestArrowConstants:
+    def test_max_timestamp_is_utc_based(self):
+        from arrow.constants import MAX_TIMESTAMP
+
+        expected = datetime.max.replace(tzinfo=timezone.utc).timestamp()
+        assert MAX_TIMESTAMP == expected
+
+    def test_max_timestamp_derived_constants(self):
+        from arrow.constants import MAX_TIMESTAMP, MAX_TIMESTAMP_MS, MAX_TIMESTAMP_US
+
+        assert MAX_TIMESTAMP_MS == MAX_TIMESTAMP * 1000
+        assert MAX_TIMESTAMP_US == MAX_TIMESTAMP * 1_000_000