fix(budget): log warning when ZoneInfo falls back 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	Feb 24, 2026 4:09pm

[LeeJuOh]

@greptileai

[greptile-apps]

Greptile Summary

This PR adds a verbose_logger.warning() call in _setup_timezone() when ZoneInfo fails to load a configured timezone and silently falls back to UTC. This addresses an observability gap from #21754 where ZoneInfo replaced the hardcoded timezone map — on environments without the tzdata package, the fallback was completely silent, leaving operators unaware their timezone configuration was being ignored.

• Adds a warning log in the except block of _setup_timezone() with an actionable message suggesting the operator check the timezone string and tzdata package installation
• Adds a mock-based unit test verifying the warning is emitted for invalid timezones
• No new dependencies; UTC fallback behavior preserved
• Import placed at module level, consistent with project conventions

Confidence Score: 5/5

• This PR is safe to merge — it only adds a warning log in an existing fallback path with no behavioral changes.
• The change is minimal and well-scoped: a single warning log added to an existing except block. No logic changes, no new dependencies, no risk of regression. The fallback behavior is preserved exactly as before. The test correctly verifies the new logging behavior using mocks.
• No files require special attention.

Important Files Changed

Filename	Overview
litellm/litellm_core_utils/duration_parser.py	Adds a verbose_logger.warning() call in the _setup_timezone() except block to log when timezone loading fails and UTC fallback occurs. Clean, minimal change with correct lazy string formatting.
tests/test_litellm/litellm_core_utils/test_duration_parser.py	Adds a mock-based test verifying the warning log is emitted when an invalid timezone is provided. No real network calls; consistent with existing test patterns.

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["tz = ZoneInfo(timezone_str)"]
    D -- Success --> E["Convert current_time to tz"]
    D -- Exception --> F["⚠️ verbose_logger.warning\n'Failed to load timezone...'"]
    F --> G["tz = timezone.utc (fallback)"]
    C --> E
    G --> E
    E --> H["Return (current_time, tz)"]

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[greptile-apps]

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[LeeJuOh]

@greptileai

[greptile-apps]

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[LeeJuOh]

@krrishdholakia Could you review this when you have a chance? This is a follow-up to #21754.

[LeeJuOh]

@greptileai

[LeeJuOh]

@krrishdholakia Rebased onto latest main and updated the PR base branch (the previous target litellm_oss_staging_02_22_2026 was already merged). Could you review this when you have a chance?

[greptile-apps]

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[shin-bot-litellm]

Review

1. Does this PR fix the issue it describes?
Yes. Follow-up to #21754 — adds warning log when ZoneInfo falls back to UTC (missing tzdata package). Operators now have visibility into timezone issues.

2. Has this issue already been solved elsewhere?
No — the silent fallback was problematic.

3. Are there other PRs addressing the same problem?
No duplicates found.

4. Are there other issues this potentially closes?
Any reports of budget reset times being wrong due to unnoticed UTC fallback.

✅ LGTM — minimal change, no new dependencies, preserves fallback behavior with observability.