https://www.odoo.com/forum/help-1/question/how-to-modify-calendarview-mintime-maxtime-slotduration-152711#answer-152749

odoo.define('your_module', function (require) {
"use strict";

var CalendarModel = require('web.CalendarModel');

CalendarModel.include({
    _getFullCalendarOptions: function () {
        var res = this._super.apply(this, arguments);
        return _.extend(res, {
            minTime: '08:00:00',
            maxTime: '22:00:00',

        });
    },
});