Even if you're using VC in English, the action uses whatever culture your OS is set to.
If you want to use VC in English, just change the payloadXML so that the days of the week *phrases* are in English, but the values are in the language that your OS expects. (In the command above, the values in the weekdays.xml payload file have been left empty because they are not needed.)
If you double-click on the payload xml in your command tree, that will open the payload xml editor so that you can modify the table.