the forge component used is: 

https://www.outsystems.com/forge/component-overview/7696/fullcalendar-reactive

(I added it wrong to the description)

Hi Jorge,

One of the approaches for your use case is to define the logic to prevent the users from selecting more than one day under the selectAllow callback function definition.

Refer to the documentation: https://fullcalendar.io/docs/selectAllow

• In the Calendar block - Include the below-mentioned selectAllow callback function definition as the AdvancedOptions property field value.

Advanced Options:

selectAllow: function(selectInfo){
    //  create a day
    var oneDay = 24 * 60 * 60 * 1000;
    var startDay = selectInfo.start;
    //  FullCalendar always gives next next day of select end day, so do minus one day
    var endDay = selectInfo.end - oneDay;
    var count = Math.round(Math.abs((startDay - endDay) / oneDay));
    //  starts at 0, so add to start at 1
    var dayCount = (count + 1);
    if(dayCount < 2){
        return true;
    }else{
        return false;
    }
}

Demo screen: BasicViews

I hope this helps you!

Kind regards,

Benjith Sam