Date Time Picker doesn't render in lists or forms after changing system locale - Support and Troubleshooting

Date Time Picker doesn't render in lists or forms after changing system locale Issue The Date time picker is displayed on the top of the form and you might got the following error:

RangeError: Incorrect locale information provided at Date.toLocaleDateString ( ) at e._showMonth (GwtDateTimePicker.js:288) at e._createControls (GwtDateTimePicker.js:93) at e.initialize (GwtDateTimePicker.js:37) at new e (js_includes_doctype.jsx?v=04-06-2021_1056&lp=Fri_Jun_04_04_32_50_PDT_2021&c=24_586&lang=en.IE:3) at Array. (change_request.do?sys_id=609093db8777a8104bc0a71e3fbb3501&sysparm_record_target=change_request&sysparm_record_row=1&sysparm_record_rows=1&sysparm_record_list=active%3Dtrue^ORDERBYDESCnumber:10948) at x (js_includes_ui16_form.jsx?v=04-06-2021_1056&lp=Fri_Jun_04_04_32_50_PDT_2021&c=24_586&lang=en.IE:11945) at Object.U [as finished_cb] (js_includes_ui16_form.jsx?v=04-06-2021_1056&lp=Fri_Jun_04_04_32_50_PDT_2021&c=24_586&lang=en.IE:11945) at Array.j (js_includes_ui16_form.jsx?v=04-06-2021_1056&lp=Fri_Jun_04_04_32_50_PDT_2021&c=24_586&lang=en.IE:11945) at I (js_includes_ui16_form.jsx?v=04-06-2021_1056&lp=Fri_Jun_04_04_32_50_PDT_2021&c=24_586&lang=en.IE:11945) (anonymous) @ change_request.do?sys_id=609093db8777a8104bc0a71e3fbb3501&sysparm_record_target=change_request&sysparm_record_row=1&sysparm_record_rows=1&sysparm_record_list=active%3Dtrue^ORDERBYDESCnumber:10950 00:23:36.758

Cause The issue is caused by the property "glide.sys.language" set with a wrong value as language code for example ("en.IE" instead of "en")

Resolution Set the property "glide.sys.language" with a correct language code.