[ns] How to get the current simulation time in ns2? Or how to know the remaining time of a timer?

[matt Wood]

Dear all,
    I want to know the current time in C++ programs. Is there a
function to do this? Or, How can I get the remaining time of a running
timer? In OpNet the function simtime( ) can be used to get the current
time. But I can't find the corresponding one in the NS2.

Thank you in advance.
Bests,
Matthew Wood