fix: three character date time format code

[kaos]

✈️ Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• [-] If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

📝 Summary

Trying to use the %:z format code resulted in a ValueError.

🔥 Motivation

This PR adds a test showing the issue, along with implementation to fix it.