Problem Overview

When a user without an explicitly configured timezone in their Atlassian Account profile accesses Team Calendars (or a calendar such as Waffle Hare Schedule), calendar events fail to load. The UI displays an error indicating:

"We didn't recognize the time zone"

Under the hood, the backend request to fetch calendar events fails with HTTP 500 Internal Server Error and error code BAD_USER_TIMEZONE because the fallback/default value Etc/GMT 0 cannot be parsed by the calendar service's timezone parser.

Steps to Reproduce

1. Log in with an Atlassian account that does not have an explicit timezone configured in their profile (or where the timezone defaults to unset / Etc/GMT 0).
2. Navigate to Confluence and open Calendars (or view a space calendar / embedded Team Calendar).
3. Observe the calendar view and browser Developer Tools (Network tab).

Expected Results

• Team Calendars should gracefully default to UTC when a user has no timezone configured in their profile.

• Calendar events should load normally without throwing errors.

Actual Results

• The calendar interface displays a banner/error: "We didn't recognize the time zone".

• The network request to /rest/calendar-services/1.0/calendar/events.json returns:
   {
  Unknown macro: {HTTP/1.1 500 Internal Server Error { "error": "BAD_USER_TIMEZONE", "message": "Cannot parse timezone: Etc/GMT 0"}}}

• Events fail to populate on the calendar.

Workaround

Affected users can manually set an explicit timezone on their Atlassian profile:

1. Navigate to Atlassian Account Profile Settings.
2. Under Preferences / Time zone, select their local timezone (or UTC).
3. Refresh the Confluence Team Calendars page