Fix non IANA timezone in Time server

[ababino]

Description

If system timezone is not in the IANA standard, these changes will set the timezone based on the UTC offset.
This fixes #489, #612, and #786.
The solution is better than PR #925 because it will not fail even if datetime.now() tzone is not IANA.
The solution is also better than PR #320 because it does not relies on hardcoded mappings.

Server Details

• Server: Time
• Changes to: tools

Motivation and Context

It doesn't work with my local setup unless the --local-timezone flag is specified.

How Has This Been Tested?

With Claude Desktop

Breaking Changes

No

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My changes follows MCP security best practices
• I have updated the server's README accordingly
• I have tested this with an LLM client
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have documented all environment variables and configuration options

Additional context

[olaservo]

Thanks for the PR! I wonder if we should incorporate the tzlocal approach from 925 as the primary approach and then do fallbacks in this order:

First attempt to use tzlocal (from PR #925) to cover platform-specific names

First fallback: Try direct ZoneInfo conversion, for cases where a valid IANA name is provided

Final fallback: Then use UTC offset matching like you have in this PR, to handle the remaining scenarios

What do you think?

[domdomegg]

Superceded by #1761