Keep Several Calendars Blocked for Each Other
The most common professional setup is not two calendars, it is four or five: a couple of client tenants, an employer account, a personal Google or iCloud calendar. The thing you actually want is simple, every one of them should show busy wherever any of the others has a meeting, but getting there one connection at a time means an Add connection visit for every pair: six separate visits for four calendars.
Why every pair, and not just a chain
Calendar Family never forwards a synced copy onward. If calendar A syncs into calendar B, the copy that lands on B does not then flow on to calendar C, so a chain (A to B to C) leaves C blind to A. Keeping three calendars blocked for each other genuinely needs three connections: A-B, A-C and B-C. That is not a limitation Connect several works around, it is the reason the page exists: it creates exactly the missing pairs for the calendars you tick, nothing more and nothing less, so it cannot create a duplicate or an echo.
One page, not one connection at a time
Once you have three or more calendars connected, a Connect several button sits beside Add calendar and Add connection.
- Click Connect several.
- Tick the calendars to keep blocked for each other - the same calendar cards you already know, each in its own colour.
- Answer one question, What to share - Free/busy only by default, or choose All details or Titles only for the whole batch.
- Check the live preview. Pairs that already have a connection show grey and are left alone; the pairs about to be created are highlighted.
- Press the button, which always tells you exactly how many it is about to add - "Add 2 connections" - so there is no guessing what is about to happen.
What it actually creates
Every new connection is two-way, so a meeting added on any one calendar shows as busy on all the others you ticked. The one exception is a calendar you can only read from: a read-only calendar cannot accept events written back to it, so its connections are created one-way, outward only, and the preview marks that pair "shares only" instead of pretending it can be two-way. The whole batch is created in a single transaction, so if anything goes wrong partway through, nothing is left half-created.
How fast it settles
Creating several connections at once means more to reconcile than a single Add connection does, so the first pass across every new pair can take a few minutes rather than being instant. Once that settles, each connection keeps working the same way the rest of Calendar Family does: Google and Microsoft push a change notification the moment something moves, so a new meeting typically shows as busy everywhere else within about a minute, while an Apple iCloud calendar is checked every 15 minutes instead, since Apple gives third-party apps no equivalent notification.
Still free
Connect several does not sit behind a paid plan or a limit on how many calendars you can block for each other - it is the free tier, applied to every pair at once instead of one at a time.
The result
Tick the calendars, answer one question, and the busy time you would otherwise have wired up pair by pair is in place everywhere it needs to be.