fix(budget): log warning on timezone fallback to UTC

[LeeJuOh]

Relevant issues

Follow-up to #21754

Pre-Submission checklist

• I have Added testing in the tests/litellm/ directory, Adding at least 1 test is a hard requirement - see details
• My PR passes all unit tests on make test-unit
• My PR's scope is as isolated as possible, it only solves 1 specific problem
• I have requested a Greptile review by commenting @greptileai and received a Confidence Score of at least 4/5 before requesting a maintainer review

Type

🐛 Bug Fix

Changes

In #21754, the hardcoded timezone_map was replaced with ZoneInfo. On environments without the tzdata package, ZoneInfo throws an exception and silently falls back to UTC — operators have no way to tell their configured timezone is being ignored.

Rather than adding tzdata as a dependency, this PR adds a verbose_logger.warning() in the except block of _setup_timezone() to log when the fallback occurs.

• litellm/litellm_core_utils/duration_parser.py: Add warning log on timezone load failure
• No new dependencies, UTC fallback behavior preserved

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Project	Deployment	Actions	Updated (UTC)
litellm	Ready	Preview, Comment	Mar 7, 2026 5:26am

[LeeJuOh]

@greptileai

[greptile-apps]

Greptile Summary

This PR adds a verbose_logger.warning() call in the except block of _setup_timezone() so operators are notified when their configured timezone cannot be loaded and UTC fallback is silently applied. No behavior changes are introduced — the UTC fallback is preserved exactly as before.

• duration_parser.py: imports verbose_logger and emits a structured warning message including the offending timezone string and a hint to install tzdata.
• test_duration_parser.py: adds test_invalid_timezone_logs_warning which patches the logger, calls get_next_standardized_reset_time with a bogus timezone, asserts warning is called exactly once, and verifies the timezone string appears in the second positional argument.
• The existing test_edge_cases test exercises "NonExistentTimeZone" without mocking the logger; it will now trigger verbose_logger.warning() on each run. Since verbose_logger is controlled by litellm's log-level settings, this produces no output in default (non-verbose) test runs, but operators running tests with verbose logging enabled will see an expected warning line for that case.

Confidence Score: 5/5

• This PR is safe to merge — it is a pure observability addition with no behavioral changes to the UTC fallback path.
• The change is minimal (5 lines of production code), non-breaking, and the test correctly validates the new behavior. The fallback to UTC is preserved, and no new dependencies are introduced.
• No files require special attention.

Important Files Changed

Filename	Overview
litellm/litellm_core_utils/duration_parser.py	Adds verbose_logger import and emits a warning with the offending timezone string and tzdata hint when timezone loading fails; fallback behavior is unchanged.
tests/test_litellm/litellm_core_utils/test_duration_parser.py	New test patches verbose_logger and verifies warning is called once with the timezone string as the second positional arg; pre-existing test_edge_cases will now silently invoke the real logger on each run.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["_setup_timezone(current_time, timezone_str)"] --> B{timezone_str is None?}
    B -- Yes --> C["tz = timezone.utc"]
    B -- No --> D["ZoneInfo(timezone_str)"]
    D -- Success --> E["tz = ZoneInfo result"]
    D -- Exception --> F["verbose_logger.warning(msg, timezone_str) 🆕"]
    F --> G["tz = timezone.utc  (fallback)"]
    C --> H["Convert current_time to tz"]
    E --> H
    G --> H
    H --> I["Return (current_time, tz)"]

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_{Last reviewed commit: a9ef3cd}

[LeeJuOh]

@greptileai

[LeeJuOh]

@krrishdholakia could you review this? Follow-up to #21754.