[Feature Request] Support for local timezone display in Alertmanager UI (instead of always UTC)

[PorPlaTakKom]

Summary

Currently, the Alertmanager web UI displays all timestamps (e.g., in alerts, silences) in UTC, with no built-in option to change or localize the timezone display.

This can be confusing for users in different regions, especially in teams operating in non-UTC timezones (e.g., Asia/Bangkok, America/New_York), as they always have to mentally convert times.

Feature Request

Please consider adding a UI-level timezone switcher or auto-detect the browser’s local timezone and display all times accordingly.

Use Case

Many organizations operate in fixed timezones. When reviewing alerts or configuring silences, working in UTC causes errors and miscommunications due to timezone mismatches.

For example, in Asia/Bangkok (UTC+7), an alert timestamp like 2025-04-21T12:00:00Z appears as 7 PM local time — but this is not immediately clear from the current UI.