I want to ask my colleague till what time he is supposed to work here, and what is latest time has has worked at office, Can I ask him
What is the latest have you worked here?
Is this expression idiomatic?
Although that sentence would probably be understood by your colleague, it is not particularly idiomatic. Instead the following would be preferable:
What is the latest you've ever left the office?
I once stayed in the office until 8pm! What's the latest you've ever stayed 'til?