Hey @WilliamPorter - The date/time is driven from your app settings. I’m in the UL but just changed my test app to GMT -6 Central America.
I set the date added on the field as you have (I use this method). I then added another date/time field for updated. This is using a record rule on form submission. As the date/time is coming from the app settings it works as expected. You can’t dictate different time zones for date/time fields so something else is going on. 
You can update the date/time field with inline editing, you’ll just have to add a record rule to each field. If you have every field on your table set to inline edit then this is going to be a chore to setup. If you have a modal popup to edit the record then you only need one record rule to update the date/time field when the form is submitted.
