How do I get the date a file was last modified?

below info was copied from www.jb.man.ac.uk/~slowe/cpp/lastmod.html for my reference in future

I wanted to be able to use the date that a file was last modified, to set the filename of another file. It took me quite a while to find out how to get hold of the date and it turns out that there are three dates on UNIX/Linux. You can use the stat()function.

#include <sys/stat.h>
 
#include <unistd.h>
 
#include <time.h> 

 
struct tm* clock;    // create a time structure
 
struct stat attrib;   // create a file attribute structure
        
stat("afile.txt", &attrib);  // get the attributes of afile.txt
 
clock = gmtime(&(attrib.st_mtime)); // Get the last modified time and put it into the time structure
 

 
// clock->tm_year returns the year (since 1900)
 
// clock->tm_mon returns the month (January = 0)
 
// clock->tm_mday returns the day of the month