CalIn — ICS Calendar to Exchange Sync

Sync busy time from any ICS/iCal calendar to Microsoft Exchange as "Blocked" slots. Works with Google Calendar, iCloud, Outlook.com, Nextcloud, Fastmail, Proton Calendar, or any CalDAV server that publishes an ICS feed.

When to Use This Skill

• User asks to sync calendars, block time, or mirror busy slots
• User wants personal calendar events to block time on their work calendar
• User asks to check sync status or clear synced events
• Scheduled background sync via Heartbeat (recommended: every 5-30 minutes)

What It Does

• Fetches events (including recurring) from any HTTPS ICS feed
• Creates/updates/deletes corresponding "Blocked" events on Exchange via Microsoft Graph API
• Tracks synced events with a local mapping file — only touches what changed
• Privacy-preserving: only syncs time slots, never event titles, descriptions, or attendees

Setup