One afternoon my calendar was completely open. Presence should have been green. The problem was that I was already on the phone handling something that had never been scheduled.
Anyone looking only at my calendar would have reached the wrong conclusion. The plan said I was free. The workday said I was not.
A calendar is valuable—and incomplete
Calendars are excellent at describing planned time. They know about the meeting scheduled for two o’clock, the focus block tomorrow morning, and the appointment someone remembered to add.
They do not automatically know that a call arrived, a Google Meet started from a message, a Teams conversation moved into the browser, an edit needed uninterrupted attention, or the meeting scheduled to end twenty minutes ago is still going.
A calendar answers “What was supposed to happen?” Presence answers “Is now a good time?”
The answer needs more than one signal
Presence begins with calendar availability, but it can also consider supported live meetings, calls, recording or streaming activity, work hours, focus time, and a manual choice.
Each signal is intentionally narrow. Presence does not need call audio, meeting chat, a document title, or the name of the person on the other end. It only needs enough information to resolve a useful status.
This is why reliability is a product feature
A status display is only helpful if people learn to trust it. If it says green during a call or remains red long after a meeting ends, everyone goes back to knocking and guessing.
Building Presence has meant paying close attention to starts, endings, stale signals, meetings that run long, browser tabs that disappear, and different devices reporting different pieces of the day. Those edge cases are not side issues. They are the product.
A perfect model of someone’s day would be invasive and unnecessary. A useful status only needs a few approved signals, sensible priorities, and a reliable path back to Available.