Use Calendar Sync now →

You probably have at least two calendars — work on Google or Outlook, personal on the other one — and they don't know about each other. Which means your coworker invites you to a 4 PM Monday call, you accept it, and now you're double-booked with a therapist appointment that lives on the other calendar entirely. The fix everyone uses is to copy events back and forth manually. The fix nobody uses is the one that actually works: a one-way sync that mirrors your busy time between calendars without leaking any details.

That's what Calendar Sync does. Free, no signup to play with, and it ships with the privacy guardrail built in: by default, every mirrored event lands on the destination calendar with the title rewritten to "Busy."

What it actually does

Pick a source calendar (the one with the real event titles) and a destination calendar (the one your coworkers see). Calendar Sync watches the source for new, updated, or deleted events and copies them over. Your source calendar is never modified.

The interesting part is the rule layer. Before each event is copied, you decide what to keep and what to strip:

• Title — keep the real title or replace it with "Busy" (or anything else, including a template like [Personal] {original_title}).
• Description — keep, blank, or override.
• Location — keep, blank, or override.
• Attendees — keep the original list or strip it so nobody is listed on the copy.
• Show as — Busy, Free, or Tentative on the destination, regardless of how the source is marked.

And the conditions that decide which rule applies are arbitrary: visibility (private vs. default), attendee count, day of week, duration, organizer email, location, all-day vs. timed. You can write something like "if visibility = private, copy as 'Busy' with attendees stripped" and let everything else mirror through unchanged.

Four presets cover most cases

Most people don't want to write a rule from scratch. The tool ships with four presets you can apply with one click:

1. Mask private events as "Busy" — anything you've marked private on the source becomes a featureless "Busy" block on the destination. Default events copy through as-is.
2. Mask everything as "Busy" — the maximum-privacy option. Your destination calendar shows nothing but blocks of unavailable time.
3. Strip attendees only — keep titles and descriptions, but don't leak the guest list across calendars.
4. Show copies as Free (don't block time) — useful when you want the destination calendar to know the events exist but not treat them as conflicts.

Why a separate tool instead of just sharing a calendar

Native calendar sharing is all-or-nothing. You either give your coworker permission to see your personal calendar (with all the details) or you don't. There's no "share that you're busy but hide what you're doing" toggle, except in the form of free/busy permissions, which most people don't trust because they leak edge cases.

A separate sync layer flips the model: instead of granting permissions, you produce a sanitized copy that lives on the calendar your coworkers already have access to. They see one calendar — the work one — and it's already accurate.

The live preview is the demo

The page itself is the demo. Open it, edit the rule conditions, and a list of sample events updates instantly to show which ones would copy and which would get rewritten. No signup, no calendar connection — just play with the rule until it does what you want, then click Set up a sync when you're ready to point it at a real calendar.

Calendar Sync is free. It runs alongside the rest of Carly's free tools — group polls, booking pages, and the new MCP server — and you don't need a paid Carly account to use it.