Preserve aware datetime timezones in format_time

_python_utils_tests/test_time.py

@@ -585,3 +585,34 @@ async def letters() -> types.AsyncGenerator[str, None]:
 
     assert items == ['a', 'b', 'c']
     assert sleeps == [1, 1, 1]
+
+
+@pytest.mark.parametrize(
+    'minutes,expected',
+    [
+        (0, '2000-01-02 03:04:05+00:00'),
+        (330, '2000-01-02 03:04:05+05:30'),
+        (-210, '2000-01-02 03:04:05-03:30'),
+    ],
+)
+def test_format_time_preserves_datetime_timezone(
+    minutes: int, expected: str
+) -> None:
+    """Truncate an aware datetime without converting it to local time."""
+    value = datetime.datetime(
+        2000,
+        1,
+        2,
+        3,
+        4,
+        5,
+        123456,
+        tzinfo=datetime.timezone(datetime.timedelta(minutes=minutes)),
+    )
+    assert python_utils.format_time(value) == expected
+
+
+def test_format_time_naive_datetime_control() -> None:
+    """Keep the existing local-time representation for naive datetimes."""
+    value = datetime.datetime(2000, 1, 2, 3, 4, 5, 123456)
+    assert python_utils.format_time(value) == '2000-01-02 03:04:05'

python_utils/time.py

@@ -124,6 +124,13 @@ def format_time(
     '0:00:01'
     >>> format_time(datetime.datetime(2000, 1, 2, 3, 4, 5, 6))
     '2000-01-02 03:04:05'
+
+    Aware datetimes keep their timezone in the formatted result.
+
+    >>> format_time(
+    ...     datetime.datetime(2000, 1, 2, tzinfo=datetime.timezone.utc)
+    ... )
+    '2000-01-02 00:00:00+00:00'
     >>> format_time(datetime.date(2000, 1, 2))
     '2000-01-02'
     >>> format_time(datetime.timedelta(seconds=3661))
@@ -165,7 +172,7 @@ def format_time(
         seconds = (since_epoch - since_epoch % precision).total_seconds()
 
         try:  # pragma: no cover
-            dt = datetime.datetime.fromtimestamp(seconds)
+            dt = datetime.datetime.fromtimestamp(seconds, timestamp.tzinfo)
         except (ValueError, OSError):  # pragma: no cover
             dt = datetime.datetime.max
         return str(dt)