Please see if my answer to this similar question on the Power Automate community would help: https://powerusers.microsoft.com/t5/Using-Connectors/Excel-Office-Script-Timezone-vs-Power-Automate-Timezone/td-p/947420
Time zones are tricky in Excel and Office Scripts, especially when you are running the script with Power Automate. The gist of the solution is to "pin" to a specific time zone.