diff --git a/addons/web/static/src/js/views/calendar/calendar_model.js b/addons/web/static/src/js/views/calendar/calendar_model.js
index 1f8c9423cac..320221f1dd9 100644
--- a/addons/web/static/src/js/views/calendar/calendar_model.js
+++ b/addons/web/static/src/js/views/calendar/calendar_model.js
@@ -385,6 +385,9 @@ return AbstractModel.extend({
      * @returns {Object}
      */
     _getFullCalendarOptions: function () {
+        var week_start = _t.database.parameters.week_start || 0;
+        // calendar uses index 0 for Sunday but Odoo stores it as 7
+        week_start = week_start % 7;
         return {
             defaultView: (this.mode === "month")? "month" : ((this.mode === "week")? "agendaWeek" : ((this.mode === "day")? "agendaDay" : "agendaWeek")),
             header: false,
@@ -404,7 +407,7 @@ return AbstractModel.extend({
             monthNamesShort: moment.monthsShort(),
             dayNames: moment.weekdays(),
             dayNamesShort: moment.weekdaysShort(),
-            firstDay: _t.database.parameters.week_start,
+            firstDay: week_start,
             slotLabelFormat: _t.database.parameters.time_format.search("%H") != -1 ? 'H:mm': 'h(:mm)a',
         };
     },