SilhouSync: Calendar Blocker

Keep your personal life private and your work availability accurate—automatically and 100% offline.

SilhouSync is a local-first scheduling utility designed to synchronize availability across multiple calendars on your Android device. By placing custom "shadow" events, SilhouSync blocks slots on conflicting calendars (e.g., your Work Calendar) whenever you have commitments on other feeds (e.g., Personal, Family, or School Board calendars).

THE PROBLEM
Managing availability across multiple calendars is a constant headache. Copying events manually leads to errors, while third-party cloud-based sync tools require logging in with corporate credentials and uploading private event titles, descriptions, and locations to external servers. For corporate work profiles, this violates strict IT data privacy (MDM/DPC) regulations.

THE LOCAL-FIRST SOLUTION
SilhouSync runs entirely on your phone, reading and writing events locally through your device's native Calendar database. It requires no external cloud logins, has no remote servers, and requires no internet access permissions (android.permission.INTERNET). Your schedules remain 100% private.

KEY FEATURES

• Local-Only Processing: SilhouSync itself does not collect or transmit any calendar data off your phone. No cloud accounts or remote servers are required.
• Perfect for Work Profiles: Designed to run inside your managed profile sandbox. It syncs availability using the calendar accounts and shared feeds already configured on your device.
• Custom Privacy Masking: Choose how shadow events appear on target calendars:
- MINIMAL (Default): Masks event details entirely, showing only "Busy" or a custom tag (e.g., #work-conflict).
- SEMI-PRIVATE: Copies the original title but wipes descriptions and locations.
- FULL COPY: Syncs the complete event details (ideal for personal-to-personal syncs).
• Starvation & Loop Prevention: Intelligent signature markers and database mapping ensure that shadow syncs do not trigger infinite recursive sync loops.
• Sliding Window Recurrence Expansion: Queries calendar instances in a moving 30-day window. This handles recurring events, modified sessions, cancellations, and local timezones perfectly.
• Sync Sandbox (Dry Run): Preview proposed creations, modifications, and deletions in a simulated sandbox before altering your calendars.
• Native Conflict Alerts: Detects real (non-shadow) scheduling conflicts across calendars and alerts you via local push notifications.
• Audit Logs: Access a transparent log of the last 200 synchronization actions and background results directly inside the app.

HOW IT WORKS
1. Grant calendar read/write permissions to allow local event access.
2. Select your Source Calendar (e.g., Personal) and Target Calendar (e.g., Work).
3. Set your privacy level and optional title prefixes (e.g., #personal-conflict).
4. Save the rule. Background triggers will automatically create, update, or remove shadow events as your schedule changes.

Avoid double-booking. Protect your calendar privacy. Try SilhouSync today.