Scheduling and booking software lets customers, patients or colleagues book appointments online. It synchronises with calendars, sends reminders and often handles intake forms or payments. Organisations use it for sales meetings, consultations, services and resource planning, from a single freelancer to a multi-site practice.
The sovereignty question is less the calendar itself than what it reveals. A booking history shows who met whom, when and why, and a calendar integration gives the tool read access to the full agendas of your staff. If the provider is subject to non-EU law, as with US-based Calendly, that metadata can fall within reach of foreign authorities. Lock-in builds up quietly through embedded booking pages, widgets and links that customers have already bookmarked.
When comparing European options, look at the scope of access requested from Google or Microsoft calendars, whether the provider acts strictly as a processor under a data processing agreement, and which sub-processors are involved. Check that booking pages can run on your own domain, and that appointments, customer records and reminders can be exported in standard formats such as iCal and CSV.