When you go to the TVGuide, select one channel from the left side so that only the EPG from that channel is displayed, then you can press and hold the "down" button on your remote, and while scrolling down, the days will change.

This does not work in the RadioGuide at all.

h4. Steps to Reproduce
1. enter MyRadio
2. navigate to an radiostation on the left side
3. press okay to enter the detailed view
4. press and hold the "down" key on your remote

The day will not change.

h4. Additional Information
http://forum.team-mediaportal.com/bugreports-74/radio-guide-only-some-hours-85327/