Looking on the internet deeply has found these results:

What time are you on? is the most popular phrase on the web.

Till what time are you on? 12 results on the web	What time are you on? 1169,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
So I'm just a diversion to kill the time till you escape? You mind if I leave some of this stuff here till next time? What are you going to read People Magazine and eat at Wendy's till the end of time? Till what time were you there? Mr President, may I on your behalf ask honourable Members if they are willing to postpone the vote on this resolution till next time? What time are we going to be here till tonight? Till what time are we needed?	What time are you leaving? What time are you meeting? Eight o'clock. Till what time are we needed? What time?

Till what time are you on?

12 results on the web

What time are you on?

1169,000 results on the web

More popular!

So I'm just a diversion to kill the time till you escape?
You mind if I leave some of this stuff here till next time?
What are you going to read People Magazine and eat at Wendy's till the end of time?
Till what time were you there?
Mr President, may I on your behalf ask honourable Members if they are willing to postpone the vote on this resolution till next time?
What time are we going to be here till tonight?
Till what time are we needed?