Is it a Virus?
NO - Safe
Typically located in C:\Program Files\CalendarSync\calendar-sync.exe
Warning
Usually legitimate, but verify signature
Check digital signature from Calendar Sync, Inc.
Can I Disable?
YES
Disabling will stop sync until re-enabled
What is calendar-sync.exe?
calendar-sync.exe is the background service responsible for syncing calendar data between your local calendar app and supported cloud providers (e.g., Google Calendar, Microsoft 365). It runs periodically to fetch updates, apply changes, and maintain consistency across devices, all while staying isolated from your main apps for safety.
The process operates as a small Windows service with a dedicated sync thread. It uses OAuth tokens to call cloud APIs, resolves conflicts via last-writer-wins rules, and stores session data in the OS credential store for security.
Quick Fact: Calendar synchronization services were popularized to keep multi-device calendars in sync with minimal user intervention.
Types of Calendar Sync Processes
- Sync Manager Process: Orchestrates scheduled and on-demand sync tasks
- Renderer/Driver Process: Handles API calls and token refreshes in a sandboxed context
- Background Listener: Monitors cloud webhook updates for real-time changes
- Conflict Resolver: Applies rules to merge conflicting events
- Telemetry/Diagnostics: Collects non-personal health data to improve reliability
- UI Helper: Integrates with calendar apps to reflect changes
Is calendar-sync.exe Safe?
Yes, calendar-sync.exe is safe when it is the legitimate file from Calendar Sync, Inc. downloaded from official sources and not altered.
Is calendar-sync.exe a Virus or Malware?
The real calendar-sync.exe is NOT a virus. Malware may imitate names; verify digital signature and location.
How to Tell if calendar-sync.exe is Legitimate or Malware
- File Location: Must be in
C:\Program Files\CalendarSync\calendar-sync.exe or C:\Program Files (x86)\CalendarSync\calendar-sync.exe. Any instance elsewhere is suspicious.
- Digital Signature: Right-click the executable -> Properties -> Digital Signatures. Should show a signature from "Calendar Sync, Inc.".
- Resource Usage: Normal usage is about 1-8% CPU and 20-60 MB memory. Persistent high usage when idle is suspicious.
- Behavior: Should run to perform sync tasks or on a scheduled basis. Unplanned network activity or persistent startup without calendar configuration is suspect.
Red Flags: If calendar-sync.exe appears in unusual folders (Temp, AppData, System32), runs when no calendar app is configured, lacks a valid signature, or uses resources constantly, scan with antivirus software. Beware of similarly named files such as "calendar-sync32.exe".
Why Is calendar-sync.exe Running on My PC?
calendar-sync.exe runs to keep your calendar data aligned across local apps and cloud providers. It starts when sync is enabled or on a scheduled basis, and may stay active to monitor for updates.
Reasons it's running:
- Active Calendar Use: You have a calendar app open and auto-sync is enabled; the service runs to sync changes.
- Background Sync Jobs: Cloud providers push changes via webhooks or scheduled tasks; the service processes these updates in the background.
- Startup and Login: Calendar sync is configured to start at Windows startup or user login for seamless updates.
- Multiple Accounts: If you connect several calendars (e.g., Google and Outlook), separate sync tasks run to coordinate events across accounts.
- Conflict Resolution: The service resolves conflicting edits across devices, which can momentarily keep the process active during merges.
Can I Disable or Remove calendar-sync.exe?
Yes, you can disable calendar-sync.exe. It is safe to disable if you do not use cloud calendar syncing, and you can uninstall the component if you prefer another solution.
How to Stop calendar-sync.exe
- Pause or End Tasks: In Task Manager, locate calendar-sync.exe and End Task. If a service, stop its related scheduled task.
- Disable Startup: Task Manager -> Startup tab -> Disable Calendar Sync
- Turn Off Background Sync: Calendar app settings -> Accounts -> disable automatic sync
- Uninstall Component: Control Panel or Settings -> Apps -> Calendar Sync -> Uninstall
- Verify No Residual Services: Check Services.msc for any calendar-sync related services and disable if present
How to Uninstall Calendar Sync
- ✔ Windows Settings → Apps → Apps & Features → Calendar Sync → Uninstall
- ✔ Control Panel → Programs → Uninstall a program → Calendar Sync → Uninstall
- ✔ Restart the machine after uninstall to ensure all components are removed
Common Problems: High CPU or Memory Usage
If calendar-sync.exe is consuming excessive resources:
Common Causes & Solutions
- Large number of calendars or events: Limit synchronized calendars or archive old events; enable selective syncing for essential calendars
- Many background tasks from multiple accounts: Review connected accounts and disable nonessential syncs; consolidate accounts where possible
- Outdated calendar client or driver: Update calendar client and calendar-sync component to the latest version
- Corrupted cache or local data: Clear app cache or reset the calendar sync data; back up before resetting
- Conflicting or duplicated events: Run conflict resolution settings or manually merge duplicates in the calendar app
- Antivirus/firewall interference: Ensure calendar-sync.exe is allowed through firewall and not blocked by antivirus
Quick Fixes:
1. Open Task Manager to identify high-usage tasks related to calendar-sync.exe
2. Restart the calendar services or the system if prompted
3. Clear calendar cache in your calendar app
4. Update Calendar Sync and the calendar client to the latest version
5. Whitelist calendar-sync.exe in antivirus/firewall settings
Frequently Asked Questions
Is calendar-sync.exe a virus?
No, the legitimate calendar-sync.exe is a real synchronization service from Calendar Sync, Inc. Verify its location at C:\Program Files\CalendarSync and ensure the digital signature matches Calendar Sync, Inc.
Why is calendar-sync.exe using so much CPU?
High CPU can occur when syncing large numbers of events, syncing from multiple accounts, or when conflicts are being resolved. Check the calendar app for heavy calendars and review sync settings.
How can I verify calendar-sync.exe is legitimate?
Check file location (C:\Program Files\CalendarSync\calendar-sync.exe), inspect the digital signature (Properties > Digital Signatures should show Calendar Sync, Inc.), and ensure network activity aligns with scheduled syncs.
Can I disable calendar-sync.exe from starting at boot?
Yes. Use Task Manager → Startup tab to disable Calendar Sync, or stop related services. This will prevent automatic syncing until you re-enable it.
What should I do if sync fails or misses events?
Check account connections, re-authenticate tokens, ensure cloud service access is allowed, update the app, and run a manual sync. Review the event history for conflicts.
How do I uninstall calendar-sync.exe?
Use Windows Settings → Apps → Apps & Features → Calendar Sync → Uninstall. After uninstall, restart your PC and verify calendar data remains intact in your calendar apps.