diff --git a/addons/web/models/ir_http.py b/addons/web/models/ir_http.py
index 73a83664683..a1fa58ef81d 100644
--- a/addons/web/models/ir_http.py
+++ b/addons/web/models/ir_http.py
@@ -5,8 +5,6 @@ import json
 
 from odoo import models
 from odoo.http import request
-import pytz
-import datetime
 
 import odoo
 
@@ -26,7 +24,6 @@ class Http(models.AbstractModel):
         version_info = odoo.service.common.exp_version()
         return {
             "session_id": request.session.sid,
-            "tzOffset": self._context.get('tz') and datetime.datetime.now(pytz.timezone(self._context['tz'])).utcoffset().total_seconds() / 60 or False,
             "uid": request.session.uid,
             "is_system": request.env.user._is_system(),
             "is_superuser": request.env.user._is_superuser(),
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');
diff --git a/addons/web/static/tests/fields/basic_fields_tests.js b/addons/web/static/tests/fields/basic_fields_tests.js
index a1aa5958009..35fa05a8eab 100644
--- a/addons/web/static/tests/fields/basic_fields_tests.js
+++ b/addons/web/static/tests/fields/basic_fields_tests.js
@@ -1589,7 +1589,9 @@ QUnit.module('basic_fields', {
               date_format: '%m/%d/%Y',
             },
             session: {
-                tzOffset: 120 // Should be ignored by date fields
+                getTZOffset: function () {
+                    return 120; // Should be ignored by date fields
+                },
             },
         });
 
@@ -1634,7 +1636,9 @@ QUnit.module('basic_fields', {
               date_format: '%m/%d/%Y',
             },
             session: {
-                tzOffset: -120 // Should be ignored by date fields
+                getTZOffset: function () {
+                    return -120; // Should be ignored by date fields
+                },
             },
         });
 
@@ -1663,7 +1667,9 @@ QUnit.module('basic_fields', {
                 date_format: '%m/%d/%Y',
             },
             session: {
-                tzOffset: 0
+                getTZOffset: function () {
+                    return 0;
+                },
             },
         });
 
@@ -1752,7 +1758,9 @@ QUnit.module('basic_fields', {
                 time_format: '%H:%M:%S',
             },
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
         });
 
@@ -1809,7 +1817,9 @@ QUnit.module('basic_fields', {
                 time_format: '%H:%M:%S',
             },
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
         });
 
@@ -1879,7 +1889,9 @@ QUnit.module('basic_fields', {
                 time_format: '%H:%M:%S',
             },
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
         });
 
@@ -1924,7 +1936,9 @@ QUnit.module('basic_fields', {
                 time_format: '%H:%M:%S',
             },
             session: {
-                tzOffset: -240,
+                getTZOffset: function () {
+                    return -240;
+                },
             },
         });
 
@@ -1966,7 +1980,9 @@ QUnit.module('basic_fields', {
                 time_format: '%H:%M:%S',
             },
             session: {
-                tzOffset: -240,
+                getTZOffset: function () {
+                    return -240;
+                },
             },
         });
 
diff --git a/addons/web/static/tests/fields/field_utils_tests.js b/addons/web/static/tests/fields/field_utils_tests.js
index 922c9f3a79c..a0284798553 100644
--- a/addons/web/static/tests/fields/field_utils_tests.js
+++ b/addons/web/static/tests/fields/field_utils_tests.js
@@ -4,6 +4,7 @@ odoo.define('web.field_utils_tests', function (require) {
 var core = require('web.core');
 var session = require('web.session');
 var fieldUtils = require('web.field_utils');
+var testUtils = require('web.test_utils');
 
 QUnit.module('fields', {}, function () {
 
@@ -63,6 +64,31 @@ QUnit.test("format_datetime", function (assert) {
     assert.strictEqual(str, moment(date).format("MM/DD/YYYY HH:mm:ss"));
 });
 
+QUnit.test("format_datetime (with different timezone offset)", function (assert) {
+    assert.expect(2);
+
+    // mock the date format to avoid issues due to localisation
+    var dateFormat = core._t.database.parameters.date_format;
+    core._t.database.parameters.date_format = '%m/%d/%Y';
+    session.getTZOffset = function (date) {
+        // simulate daylight saving time
+        var startDate = new Date(2017, 2, 26);
+        var endDate   = new Date(2017, 9, 29);
+        if (startDate < date && date < endDate) {
+            return 120; // UTC+2
+        } else {
+            return 60; // UTC+1
+        }
+    };
+
+    var str = fieldUtils.format.datetime(moment.utc('2017-01-01T10:00:00Z'));
+    assert.strictEqual(str, '01/01/2017 11:00:00');
+    str = fieldUtils.format.datetime(moment.utc('2017-06-01T10:00:00Z'));
+    assert.strictEqual(str, '06/01/2017 12:00:00');
+
+    core._t.database.parameters.date_format = dateFormat;
+});
+
 QUnit.test("format_many2one", function (assert) {
     assert.expect(2);
 
diff --git a/addons/web/static/tests/fields/relational_fields_tests.js b/addons/web/static/tests/fields/relational_fields_tests.js
index fd872fe2ca7..3d6721a55df 100644
--- a/addons/web/static/tests/fields/relational_fields_tests.js
+++ b/addons/web/static/tests/fields/relational_fields_tests.js
@@ -1771,7 +1771,9 @@ QUnit.module('relational_fields', {
                 '</form>',
             res_id: 1,
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
         });
         assert.strictEqual(form.$('td:eq(0)').text(), "01/25/2017",
diff --git a/addons/web/static/tests/helpers/test_utils.js b/addons/web/static/tests/helpers/test_utils.js
index 56070453e31..0115dfc9152 100644
--- a/addons/web/static/tests/helpers/test_utils.js
+++ b/addons/web/static/tests/helpers/test_utils.js
@@ -256,8 +256,11 @@ function addMockEnvironment(widget, params) {
     var initialDebounce = DebouncedField.prototype.DEBOUNCE;
     DebouncedField.prototype.DEBOUNCE = params.fieldDebounce || 0;
     var initialSession, initialConfig, initialParameters;
+    initialSession = _.extend({}, session);
+    session.getTZOffset = function () {
+        return 0; // by default, but may be overriden in specific tests
+    };
     if ('session' in params) {
-        initialSession = _.extend({}, session);
         _.extend(session, params.session);
     }
     if ('config' in params) {
@@ -282,8 +285,8 @@ function addMockEnvironment(widget, params) {
             for (key in session) {
                 delete session[key];
             }
-            _.extend(session, initialSession);
         }
+        _.extend(session, initialSession);
         if ('config' in params) {
             for (key in config) {
                 delete config[key];
diff --git a/addons/web/static/tests/views/calendar_tests.js b/addons/web/static/tests/views/calendar_tests.js
index 6832c71b170..29e76182bb4 100644
--- a/addons/web/static/tests/views/calendar_tests.js
+++ b/addons/web/static/tests/views/calendar_tests.js
@@ -440,7 +440,9 @@ QUnit.module('Views', {
                 initialDate: initialDate,
             },
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
             mockRPC: function (route, args) {
                 if (args.method === "create") {
@@ -541,7 +543,9 @@ QUnit.module('Views', {
                 initialDate: initialDate,
             },
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
             mockRPC: function (route, args) {
                 if (args.method === "create") {
@@ -664,7 +668,9 @@ QUnit.module('Views', {
                 initialDate: initialDate,
             },
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
         });
 
@@ -728,7 +734,9 @@ QUnit.module('Views', {
                 initialDate: initialDate,
             },
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
         });
 
diff --git a/addons/web/static/tests/views/form_tests.js b/addons/web/static/tests/views/form_tests.js
index 3a1976592d7..ada05e5ed28 100644
--- a/addons/web/static/tests/views/form_tests.js
+++ b/addons/web/static/tests/views/form_tests.js
@@ -2849,7 +2849,9 @@ QUnit.module('Views', {
                 '</form>',
             res_id: 1,
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
         });
 
diff --git a/addons/web/static/tests/views/list_tests.js b/addons/web/static/tests/views/list_tests.js
index 402b59194f8..083aa349516 100644
--- a/addons/web/static/tests/views/list_tests.js
+++ b/addons/web/static/tests/views/list_tests.js
@@ -1271,7 +1271,9 @@ QUnit.module('Views', {
             data: this.data,
             arch: '<tree><field name="date"/><field name="datetime"/></tree>',
             session: {
-                tzOffset: 120
+                getTZOffset: function () {
+                    return 120;
+                },
             },
         });