ICS Timezone Fixer

Small Go-based proxy that fetches an Outlook ICS feed, normalizes Outlook TZIDs using the embedded VTIMEZONE rules, and republishes a corrected ICS feed that Google Calendar can subscribe to.

Usage

1. Deploy to Vercel.
2. Subscribe Google Calendar to:

https://<your-vercel-app>.vercel.app/api/calendar?url=<OUTLOOK_ICS_URL>

Optional override:

https://<your-vercel-app>.vercel.app/api/calendar?url=<OUTLOOK_ICS_URL>&tz_hint=Europe/Berlin

Notes

• Only outlook.office365.com is allowed as the source host.
• Windows TZIDs are mapped using the CLDR global (001) windowsZones table.
• CLDR license notice is in THIRD_PARTY_NOTICES.txt.
• If a VTIMEZONE signature matches a known IANA zone, the TZID is replaced.
• If no mapping exists, the original TZID is left untouched.
• VTIMEZONE blocks are stripped after normalization.
• The handler returns text/calendar and streams the transformed content.

Testing

go test ./...