[FIX] web: incorrect date in calendar

- Set the OS timezone to GMT-6
- Create a project task with a date deadline on D day
- The tasks appears at D-1 in the calendar

This was supposed to be fixed with 0c0fb63b0d, but actually no.

opw-1815446
opw-1828130

addons/web/static/src/js/views/calendar/calendar_model.js

@@ -611,7 +611,8 @@ return AbstractModel.extend({
         var date_start;
         var date_stop;
         var date_delay = evt[this.mapping.date_delay] || 1.0,
-            all_day = this.mapping.all_day ? evt[this.mapping.all_day] : false,
+            all_day = this.fields[this.mapping.date_start].type === 'date' ||
+                this.mapping.all_day && evt[this.mapping.all_day] || false,
             the_title = '',
             attendees = [];
 
@@ -635,8 +636,6 @@ return AbstractModel.extend({
         if (this.mapping.all_day && evt[this.mapping.all_day]) {
             date_stop.add(1, 'days');
         }
-        var isAllDay = this.fields[this.mapping.date_start].type === 'date' ||
-                        this.mapping.all_day && evt[this.mapping.all_day] || false;
         var r = {
             'record': evt,
             'start': date_start,
@@ -644,7 +643,7 @@ return AbstractModel.extend({
             'r_start': date_start,
             'r_end': date_stop,
             'title': the_title,
-            'allDay': isAllDay,
+            'allDay': all_day,
             'id': evt.id,
             'attendees':attendees,
         };

addons/web/static/tests/views/calendar_tests.js

@@ -1571,7 +1571,7 @@ QUnit.module('Views', {
     });
 
     QUnit.test('set event as all day when field is date', function (assert) {
-        assert.expect(1);
+        assert.expect(2);
 
         this.data.event.records[0].start_date = "2016-12-14";
 
@@ -1595,9 +1595,16 @@ QUnit.module('Views', {
             viewOptions: {
                 initialDate: initialDate,
             },
+            session: {
+                getTZOffset: function () {
+                    return -480;
+                }
+            },
         });
         assert.strictEqual(calendar.$('.fc-day-grid .fc-event-container').length, 1,
             "should be one event in the all day row");
+        assert.strictEqual(calendar.model.data.data[0].r_start.date(), 14,
+            "the date should be 14");
         calendar.destroy();
     });