we're adding a new field "product renewal date" but not exactly sure how we would write it out for the data upload. Is there a specific way you can upload dates into Marketo? Can we set the way we want the date to show? Anyone know?
Format dates and datetimes using ISO 8601 W3C profile: Date and Time Formats
Remember that a given instant may be represented using different formats depending on the value of other lead fields (like home country and/or preferred language). So there can't be (or shouldn't be) a single output format associated with a date/datetime field.