On-site time varies by service and by vehicle. The vehicle stays in the shop's bay for the whole procedure.
The honest answer is, "less time than it took the last vendor." But the honest answer also depends on what is being calibrated, and planning the bay around realistic numbers saves a delivery promise from slipping.
What stretches the timeline
Three things slow a calibration: an unstable surface that has to be re-leveled, an OEM procedure that requires a dynamic drive in conditions that are not currently available, and a sensor that fails calibration and needs to be inspected for prior damage. A good vendor flags all three before they cost the bay an extra hour.
How to plan around it
Treat the calibration as its own operation on the production schedule, with the same care as paint or alignment. Booking it the day you write the supplement, instead of the day the car is ready to deliver, is the single biggest predictor of an on-time release.
Focal ADAS handles it on-site, same day, from Seattle to Tacoma.
Put calibration on autopilot.
Request a calibration in 60 seconds. A reply with an arrival window comes back within the hour.