What Is a Calendar Conflict?
TL;DR
A calendar conflict is an overlap between two events on the same calendar, which in a booking context means a slot was offered and taken while it was already busy. It is almost always a sync problem: the scheduling tool acted on availability that had gone stale.
What causes a calendar conflict?
Stale availability, most often. A tool that cached free time, or that reads only one of the calendars a person actually uses, offers a slot already taken, and the conflict is created at the moment of booking rather than discovered afterwards.
The rest are time zone arithmetic across a daylight saving change, an all-day event the tool treats as free, and a second calendar, personal or from another workspace, that was never connected in the first place.
How is double-booking prevented?
By reading availability from the live calendar at the moment a slot is confirmed, not only when the page was first rendered. The gap between those two moments is where every booking race condition lives.
Connecting every calendar that holds real commitments is the other half. Availability is only as accurate as the least complete calendar the tool can see, so one personal calendar left out keeps producing conflicts nobody can explain.
Frequently asked questions
Because the conflicting event usually sits on a calendar the tool cannot see, or it was declined rather than removed. Checking which accounts are connected, and whether tentative events count as busy, resolves most of these cases.