__TIMESTAMP__ is a preprocessor macro that expands to current time (at compile time) in the form Ddd Mmm Date hh::mm::ss yyyy, where the time is in 24 hour time, Ddd is the abbreviated day, Mmm is the abbreviated month, Date is the current day of the month (1-31), and yyyy is the four digit year. For example "Wed Jan 18 22:29:12 2012". The __TIMESTAMP__ macro can be used to provide information about the particular moment a binary was built.
void printBuildDateTime ()
    cout << __TIMESTAMP__ << endl;
You can also use the __DATE__ macro to get the current date, or the __TIME__ macro to get the current time.


C preprocessor tutorial