you must ensure that the Windows user account that is to be used to execute the task has a User Personalisation record with the correct Language ID.7177 is the English - Southern Africa language ID and If you do not have a record, or you use the English (United States) setting then you will find date fields are validated using the US M/dd/YYYY date format. so either change/add a record to the User Personalisation table or format your date string like this mmddyyyy