__DATE__ is a preprocessor macro that expands to current date (at compile time) in the form mmm dd yyyy (e.g. "Jan 14 2012"), as a string. The __DATE__ macro can be used to provide information about the particular moment a binary was built.
void printBuildDate ()
    cout << __DATE__ << endl;
You can also use the __TIME__ macro to get the current time.


C preprocessor tutorial