I also bumped into the problem with time part shown in RadDatePicker :(
I have radiobutton which makes postback without response redirect.
So, when I come to the page containing RadDatePicker on such PostBack, without setting initial value on non-postback loading, I get time part shown. I tried to fight it, but in vain.
So I need to invent some dirty hack to cut time part. I see no other way around, I need postback.
The most sad thing is that sometimes I am able to reproduce this stuff and sometimes it's suddenly getting ok without any code changes!
And one more: the same filter sometimes displays time in american style (AM/PM), sometimes in european - also no some special settings...
UPDATE: I had to force TimeFormat to string.Empty for one page and to "HH:mm" (I use such format everywhere) for others in PreRender event (Mr. Dirty Hack)