[FIX] web: core: offset in to_utc

Take a PyDateTime representing the moment "2022-10-17 00:00:00" in
the timezone of Brussels. Trying to get the related utc moment through
to_utc gives wrongly "2022-10-16 23:00:00". This happens because the
months are not numbered in the same way in Date or PyDateTime, so that
in October for example, the offset applied was that of November which is
-60 instead of -120 (summer/winter change). We fix that problem.

closes odoo/odoo#103561

X-original-commit: a11e1fb5f702400fe51938362fe3f24570977ba9
Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>
Signed-off-by: Mathieu Duckerts-Antoine <dam@odoo.com>

addons/web/static/src/core/py_js/py_date.js

@@ -489,7 +489,7 @@ export class PyDateTime {
      * @returns {PyDateTime}
      */
     to_utc() {
-        const d = new Date(this.year, this.month, this.day, this.hour, this.minute, this.second);
+        const d = new Date(this.year, this.month -1, this.day, this.hour, this.minute, this.second);
         const timedelta = PyTimeDelta.create({ minutes: d.getTimezoneOffset() });
         return this.add(timedelta);
     }

addons/web/static/tests/core/py_js/py_date_tests.js

@@ -71,6 +71,24 @@ QUnit.module("py", {}, () => {
             assert.strictEqual(JSON.stringify(evaluateExpr(expr)), `"2021-09-16 18:00:00"`);
         });
 
+        QUnit.test("to_utc in october with winter/summer change", (assert) => {
+            patchDate(2021, 9, 17, 10, 0, 0);
+            patchWithCleanup(Date.prototype, {
+                getTimezoneOffset() {
+                    const month = this.getMonth() // starts at 0;
+                    if (10 <= month || month <= 2) {
+                        //rough approximation
+                        return -60;
+                    } else {
+                        return -120;
+                    }
+                },
+            });
+            const expr =
+                "datetime.datetime(2022, 10, 17).to_utc()";
+            assert.strictEqual(JSON.stringify(evaluateExpr(expr)), `"2022-10-16 22:00:00"`);
+        });
+
         QUnit.test("datetime.datetime.combine", (assert) => {
             const expr =
                 "datetime.datetime.combine(context_today(), datetime.time(23,59,59)).strftime('%Y-%m-%d %H:%M:%S')";