Good work, and it has a nice feel to it. I look forward to seeing the 24h and keyboard access todo's sorted!
I did something like this a while back for selecting year, month and day. (Yours looks better though!) Because the row of 31 days was so long I arranged them in two rows of 15. I dare say you could enhance yours to pick dates instead (or as well?!) When you tackle the 24h layout you could offer the option of 2 rows of 12 to save horizontal space. some people will prefer it in some circumstances. Cheers, George Adamson