mutateRelationshipDataBeforeFillUsing

How to show date in d/m/Y format without datepicker coming from a relationship? DatePicker solves the formatting, but users with visual difficulties find it difficult to use the picker, that's why they don't want to use the datepicker, I tried using mutateRelationshipDataBeforeFillUsing but it doesn't work for relationship, mutateRelationshipDataBeforeSaveUsing works for saving, but mutateRelationshipDataBeforeFillUsing doesn't for filling