Might you be confusing yourself/recorder by using 24hr notation and 'am/pm' notation at the same time. Generally only one can be used at a time. Try entering 3pm.
JJ but you said you are using AM and PM, if that is the case finish time would be 1.15, not 13.15. Do you still have instructions for Sky unit to refer to?
like I tried 12.30 pm to 16.30 - it wouldn't insert 6
I am wondering when you go back to the listings of the radio and you try to jump ahead for tomorrow next day and so on. It won't go further than today. I would say that's the problem. Radio wont go ahead at the listings