You're in Berlin, your client is in New York, your second calendar is in Pacific Time. Conflict detection has to normalize all of this. This is a solved problem with the right tool configuration.
The root cause
Most multi-calendar conflict bugs trace to one of three root causes: caching (the tool snapshots availability and serves stale data), scope mismatch (the OAuth permission doesn't include the calendar that's busy), or aggregation error (multiple free/busy results weren't merged correctly).
The Cal Clear mitigation
Cal Clear doesn't cache — every booking-page request triggers a fresh free/busy query. OAuth scope is freeBusy-only per-account, verified on connect. Aggregation uses a straightforward interval merge that's been load-tested against extreme cases (50+ recurring events per day).
What to verify with any tool
Book a test slot during a known busy time across each of your calendars. If the slot is offered, the tool's conflict check is broken for your setup. Don't rely on marketing copy — test.
Part of the multi-calendar scheduling pillar guide.
Frequently Asked Questions
How often does Cal Clear actually miss a conflict?
In our internal testing, less than 1 in 10,000 requests. The system fails closed — if any component is unreachable, the affected calendar's availability isn't served, avoiding the false-positive case.
What if one of my Google accounts is temporarily down?
Cal Clear detects the failure and stops offering slots for that account's availability until the connection recovers. Better to show fewer slots than to allow an unchecked double-booking.
Unlimited calendars on every booking, free
Cal Clear checks every connected Google account on every booking-page request. Free forever, no tier gating.