It call get_time() function (method?) and then call to_string() method of whatever is returned (probably std::string). Then call c_str() on it.
It is roughtly equivalent to:
1 2 3
auto x = get_time();
auto y = x.to_string();
y.c_str();
I want to warn that if there is std::string involved, then pointer returned by c_str() will become invalid immediately after this expression finishes. Be careful with it.