I have a variable holding my minDate, for example 12:30. When i first enter into the calender control, I can change the time to before min Date once, by clicking the down arrow on the control:

This is p-calender:

<p-calendar       [timeOnly]="true" id="aEnd"
                  [(ngModel)]="dailyEntry.bookEndTime"
                  (ngModelChange)="onAttendanceChange()"
                  [minDate]="dailyEntry.bookStartTime!"
                  [defaultDate]="dailyEntry.bookStartTime!"
                  [style]="{width: '100%'}"></p-calendar>

I expected that I am not able to go below the minDate when clicking the arrows pointing down. But when I click them the first time I can go below minDate. After the first click the minDate is enforced.