fix(cost): evaluate off-peak windows in UTC for timezone-aware inputs

_is_within_off_peak_window used current_time.time(), which drops tzinfo, so a caller passing a non-UTC aware datetime had the window compared against local wall-clock instead of UTC. That silently mispriced off-peak requests. Normalize aware datetimes to UTC before comparing; naive datetimes stay as-is per the documented UTC contract. Added a regression test with a UTC+8 datetime that fails without the fix

litellm/litellm_core_utils/llm_cost_calc/utils.py

@@ -300,6 +300,8 @@ def _is_within_off_peak_window(off_peak_hours_utc: str | list[str], current_time
     """
     if current_time is None:
         current_time = datetime.now(timezone.utc)
+    elif current_time.tzinfo is not None:
+        current_time = current_time.astimezone(timezone.utc)
     now = current_time.time()
     windows = [off_peak_hours_utc] if isinstance(off_peak_hours_utc, str) else off_peak_hours_utc
     for window in windows:

tests/test_litellm/litellm_core_utils/llm_cost_calc/test_llm_cost_calc_utils.py

@@ -3983,6 +3983,19 @@ def test_is_within_off_peak_window_multiple_windows():
     assert _is_within_off_peak_window([], datetime(2026, 1, 1, 14, 0, tzinfo=timezone.utc)) is False
 
 
+def test_is_within_off_peak_window_normalizes_timezone_aware_input():
+    from datetime import datetime, timedelta, timezone
+
+    # A caller may pass a non-UTC aware datetime; the window is UTC and must be
+    # evaluated in UTC, not against the caller's wall-clock. 09:00 at UTC+8 is
+    # 01:00 UTC, inside the 01:00-05:00 window.
+    tz_plus_8 = timezone(timedelta(hours=8))
+    assert _is_within_off_peak_window("01:00-05:00", datetime(2026, 1, 1, 9, 0, tzinfo=tz_plus_8)) is True
+    assert _is_within_off_peak_window("01:00-05:00", datetime(2026, 1, 1, 12, 0, tzinfo=tz_plus_8)) is True
+    # 06:00 at UTC+8 is 22:00 UTC the previous day, outside the window
+    assert _is_within_off_peak_window("01:00-05:00", datetime(2026, 1, 1, 6, 0, tzinfo=tz_plus_8)) is False
+
+
 def test_is_within_off_peak_window_malformed_returns_false():
     from datetime import datetime, timezone