4 files changed, 23 insertions, 16 deletions

diff --git a/addons/web/static/src/js/core/session.js b/addons/web/static/src/js/core/session.js
index c98ff7fbe9a..033d7995c9c 100644
--- a/addons/web/static/src/js/core/session.js
+++ b/addons/web/static/src/js/core/session.js
@@ -285,10 +285,6 @@ var Session = core.Class.extend(mixins.EventDispatcherMixin, {
         var result = _.extend({}, window.odoo.session_info);
         delete result.session_id;
         _.extend(this, result);
-        if (this.tzOffset === false) {
-            // send by server to have the user timezone and not the browser timezone
-            this.tzOffset = -new Date().getTimezoneOffset();
-        }
         return $.when();
     },
     check_session_id: function () {
@@ -410,6 +406,17 @@ var Session = core.Class.extend(mixins.EventDispatcherMixin, {
         }) ? '' : this.prefix;
         return prefix + path + qs;
     },
+    /**
+     * Returns the time zone difference (in minutes) from the current locale
+     * (host system settings) to UTC, for a given date. The offset is positive
+     * if the local timezone is behind UTC, and negative if it is ahead.
+     *
+     * @param {string || moment} date a valid string date or moment instance
+     * @returns {integer}
+     */
+    getTZOffset: function (date) {
+        return -new Date(date).getTimezoneOffset();
+    },
 });
 
 return Session;
diff --git a/addons/web/static/src/js/fields/basic_fields.js b/addons/web/static/src/js/fields/basic_fields.js
index ec04f67e270..035d24dbdf2 100644
--- a/addons/web/static/src/js/fields/basic_fields.js
+++ b/addons/web/static/src/js/fields/basic_fields.js
@@ -450,7 +450,7 @@ var FieldDateTime = FieldDate.extend({
      */
     _getValue: function () {
         var value = this.datewidget.getValue();
-        return value && value.add(-this.getSession().tzOffset, 'minutes');
+        return value && value.add(-this.getSession().getTZOffset(value), 'minutes');
     },
 
     /**
@@ -460,7 +460,7 @@ var FieldDateTime = FieldDate.extend({
      * @private
      */
     _makeDatePicker: function () {
-        var value = this.value && this.value.clone().add(this.getSession().tzOffset, 'minutes');
+        var value = this.value && this.value.clone().add(this.getSession().getTZOffset(this.value), 'minutes');
         return new datepicker.DateTimeWidget(this, {defaultDate: value});
     },
 
@@ -471,7 +471,7 @@ var FieldDateTime = FieldDate.extend({
      * @private
      */
     _renderEdit: function () {
-        var value = this.value && this.value.clone().add(this.getSession().tzOffset, 'minutes');
+        var value = this.value && this.value.clone().add(this.getSession().getTZOffset(this.value), 'minutes');
         this.datewidget.setValue(value);
         this.$input = this.datewidget.$input;
     },
diff --git a/addons/web/static/src/js/fields/field_utils.js b/addons/web/static/src/js/fields/field_utils.js
index 787f66080dd..db5cd34d8b9 100644
--- a/addons/web/static/src/js/fields/field_utils.js
+++ b/addons/web/static/src/js/fields/field_utils.js
@@ -97,7 +97,7 @@ function formatDate(value, field, options) {
     }
     if (field && field.type === 'datetime') {
         if (!options || !('timezone' in options) || options.timezone) {
-            value = value.clone().add(session.tzOffset, 'minutes');
+            value = value.clone().add(session.getTZOffset(value), 'minutes');
         }
     }
     var l10n = core._t.database.parameters;
@@ -123,7 +123,7 @@ function formatDateTime(value, field, options) {
         return "";
     }
     if (!options || !('timezone' in options) || options.timezone) {
-        value = value.clone().add(session.tzOffset, 'minutes');
+        value = value.clone().add(session.getTZOffset(value), 'minutes');
     }
     var l10n = core._t.database.parameters;
     var date_format = time.strftime_to_moment_format(l10n.date_format);
@@ -404,7 +404,7 @@ function parseDateTime(value, field, options) {
     } else {
         datetime = moment.utc(value, [pattern1, pattern2, moment.ISO_8601], true);
         if (options && options.timezone) {
-            datetime.add(-session.tzOffset, 'minutes');
+            datetime.add(-session.getTZOffset(datetime), 'minutes');
         }
     }
     if (datetime.isValid()) {
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 d2b0c02c524..ed02983d957 100644
--- a/addons/web/static/src/js/views/calendar/calendar_model.js
+++ b/addons/web/static/src/js/views/calendar/calendar_model.js
@@ -65,12 +65,12 @@ return AbstractModel.extend({
                 end.startOf('day').add(-1, 'days');
             } else {
                 // default hours in the user's timezone
-                start.hours(7).add(-this.getSession().tzOffset, 'minutes');
-                end.hours(19).add(-this.getSession().tzOffset, 'minutes');
+                start.hours(7).add(-this.getSession().getTZOffset(start), 'minutes');
+                end.hours(19).add(-this.getSession().getTZOffset(end), 'minutes');
             }
         } else {
-            start.add(-this.getSession().tzOffset, 'minutes');
-            end.add(-this.getSession().tzOffset, 'minutes');
+            start.add(-this.getSession().getTZOffset(start), 'minutes');
+            end.add(-this.getSession().getTZOffset(end), 'minutes');
         }
 
         if (this.mapping.all_day) {
@@ -599,8 +599,8 @@ return AbstractModel.extend({
             date_stop = date_start.clone().add(date_delay,'hours');
         }
 
-        date_start.add(this.getSession().tzOffset, 'minutes');
-        date_stop.add(this.getSession().tzOffset, 'minutes');
+        date_start.add(this.getSession().getTZOffset(date_start), 'minutes');
+        date_stop.add(this.getSession().getTZOffset(date_stop), 'minutes');
 
         if (this.mapping.all_day && evt[this.mapping.all_day]) {
             date_stop.add(1, 'days');