Currently, the system displays all sub-calendars, but only allows selecting one at a time for availability checks. This leads to inaccurate availability results, as appointments marked in other sub-calendars are not taken into account and time slots may incorrectly appear as free.
To improve accuracy, the availability check should include multiple sub-calendars simultaneously. This way, any overlapping or conflicting appointments across all relevant calendars can be properly considered, preventing scheduling conflicts and ensuring a more reliable overview of true availability.