Preheat the slow cooker if necessary; see the manufacturer's instructions. Mix together the butter, sugar, cinnamon and orange rind until smooth, then stir in the chopped ginger and dates.
Trim a thin slice off the bottom of the apples, if needed, so that they will stand up without rolling over, then cut a thick slice off the top of each and reserve for later. Using a small knife, cut away the apple core to leave a cavity for the stuffing.
Divide the date mixture into 4 and press a portion into each apple cavity, spreading it over the top cut edge of the apple if it won't all fit in. Replace the apple lids and then put the apples into the slow cooker pot. Pour the apple juice into the base of the pot, cover with the lid and cook on low for 3–4 hours or until the apples are tender.
Lift the apples carefully out of the slow cooker and serve in shallow dishes with the sauce spooned over and a drizzle of hot custard or cream.