as to when/about when

[Vladv1]

Which one sounds better? I am uncertain as to when the meeting starts/I am uncertain about when the meeting starts.

 

[Tarheel]

I would probably use the second one. Having said that, in my humble opinion either is possible.

 

[jutfrank]

To me, the first, though it would depend on the register. In casual every day speech, I don't think the word 'uncertain' is a likely choice. A lot of people would say 'I'm not sure' or 'I don't know'.