How to challenge a timed game

I'm having trouble challenging a friend for a timed game of 15 or 30 minutes.  The options seem to be in terms of days-per-move.  Is there anyway that I can issue a challenge for, say, a 15 minute game?  

You have almost exclusively used the "Live Chess" portoin of this site. How have you not worked out that to do the above you should be there???

Thanks, but I'm afraid that I don't understand your advice.  How can I challenge a friend to a 30 minute game on "Live Chess"?

I think you both have to be in live chess at the same time. Click the friends tab. You should be able to challenge your friend from there.

I don't have any friends in live chess right now to confirm this, but I'm pretty sure that's how it works

Thanks PHudson.  I thought I had tried that, but will do so again.

No, simply do /challenge s0me0ne 30 0 u

remove u for rated

change 0 to some number for additional time

change 30 for a new time