We don’t currently support changing the start day for weeks in Embeddable to anything other than Monday, but there is a workaround for it that will allow you and your users to select other options. You can extend the granularity type via your Cube models and a custom type file, as described here, to add a “Week starting on [day]” option to the picker. This won’t replace the existing “weekly” option, which will still consider Monday the start of the week, but it will make your other choice(s) available to your users.