Pit record
mcp-server-time crashes when the local timezone is an abbreviation like EDT/PDT/CEST
uvx mcp-server-time can crash with a zoneinfo load error when the local timezone resolves to a non-IANA abbreviation (EDT/PDT/CEST), typically under DST, because Python zoneinfo only loads canonical IANA names. Pass a valid IANA name with --local-timezone (e.g. America/New_York).
Markdown mirror | Canonical source
Fast answer
Problem: uvx mcp-server-time traceback through zoneinfo/_common.py load_tzdata failing to load the timezone
Root cause: The server resolves the local timezone, but the platform reports a non-IANA abbreviation (e.g. EDT).
Fix first: Pass an explicit IANA timezone with --local-timezone.
Verify: Start the server with an explicit IANA timezone.
Queries this answers
- Time server fails under EDT timezone use --local-timezone with an IANA name
- Time server fails under EDT timezone (use --local-timezone with an IANA name) fix
- Time server fails under EDT timezone (use --local-timezone with an IANA name) root cause
- mcp-server-time crashes when the local timezone is an abbreviation like EDT/PDT/CEST
- mcp-server-time crashes when the local timezone is an abbreviation like EDT/PDT/CEST fix
- mcp-server-time crashes when the local timezone is an abbreviation like EDT/PDT/CEST root cause
- how to fix mcp-server-time crashes when the local timezone is an abbreviation like EDT/PDT/CEST
- mcp-server local timezone abbreviation like edt pdt cest
Record metadata
| Status | verified |
|---|---|
| Confidence | high |
| Created | 2026-06-21 |
| Updated | 2026-06-21 |
| Last verified | 2026-06-21 |
| Affected tools | mcp-server, claude-desktop |
| Tags | mcp, server-time, timezone, zoneinfo, iana, uvx |
Common search queries
- mcp-time-server-invalid-local-timezone
- mcp time server invalid local timezone
- mcp-server-time crashes when the local timezone is an abbreviation like EDT/PDT/CEST
- mcp-server-time crashes when the local timezone is an abbreviation like EDT/PDT/CEST fix
- mcp-server-time crashes when the local timezone is an abbreviation like EDT/PDT/CEST root cause
- server-time
- timezone
- zoneinfo
- iana
- mcp-server
- claude-desktop
- uvx mcp-server-time traceback through zoneinfo/_common.py load_tzdata failing to load the timezone
Symptoms
- uvx mcp-server-time traceback through zoneinfo/_common.py load_tzdata failing to load the timezone
- happens when DST is active and the local zone shows as an abbreviation (EDT/PDT/CEST)
- works fine in standard time for some users
Environment
| language | Python |
|---|---|
| package_manager | uv |
| constraints | platform reports a non-IANA local timezone abbreviation, zoneinfo loads only canonical IANA names |
Root cause
- The server resolves the local timezone, but the platform reports a non-IANA abbreviation (e.g. EDT).
- Python's zoneinfo only loads canonical IANA names (e.g. America/New_York), so loading the abbreviation raises and the server fails to start.
Fix
Pass an explicit IANA timezone with --local-timezone.
mcp-server-time --local-timezone America/New_YorkIn an MCP config, add --local-timezone with an IANA name to args.
Always use a region/city IANA name, never an abbreviation like EDT/PDT/CEST.
Verification
Start the server with an explicit IANA timezone.
Expected: Starts without the zoneinfo load traceback.
Workarounds
- Set the process/system timezone to a canonical IANA name.
Anti-patterns
- Passing a timezone abbreviation (EDT/PDT/CEST) instead of an IANA name.
- Relying on auto-detected local timezone on a platform that emits abbreviations during DST.
Sources
No matching fix?
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