I have an error with this fix because my timezone isn't the expected one:

[lunny]

    I  have an error with this fix because my timezone isn't the expected one:

 FAIL  web_src/js/utils.test.js > translateDay
AssertionError: expected 'dim.' to deeply equal 'lun.'
 ❯ web_src/js/utils.test.js:127:27
    125|   const originalLang = document.documentElement.lang;
    126|   document.documentElement.lang = 'fr-FR';
    127|   expect(translateDay(1)).toEqual('lun.');
       |                           ^
    128|   expect(translateDay(5)).toEqual('ven.');
    129|   document.documentElement.lang = 'pl-PL';

  - Expected   "lun."
  + Received   "dim."

I suggest the fix must considered the same timezone (UTC) for the localised test:

 
 // given a month (0-11), returns it in the documents language
 export function translateMonth(month) {
-  return new Date(Date.UTC(2022, month, 12)).toLocaleString(getCurrentLocale(), {month: 'short'});
+  return new Date(Date.UTC(2022, month, 12)).toLocaleString(getCurrentLocale(), {month: 'short', timeZone: 'UTC'});
 }
 
 // given a weekday (0-6, Sunday to Saturday), returns it in the documents language
 export function translateDay(day) {
-  return new Date(Date.UTC(2022, 7, day)).toLocaleString(getCurrentLocale(), {weekday: 'short'});
+  return new Date(Date.UTC(2022, 7, day)).toLocaleString(getCurrentLocale(), {weekday: 'short', timeZone: 'UTC'});
 }

ping @yardenshoham

Originally posted by @fsologureng in #15541 (comment)