I would like for someone so explain time.h for me please

[iLuvTofu]

Hello,

I just started c++ programming in college and there was a problem in my homework that said something about getting the total number of seconds elapsed since January 1, 1970. I think I found the answer here: http://www.cplusplus.com/reference/clibrary/ctime/time/ but the thing is that I don't want to just copy the answer; I want to understand it. If someone could please take the time to fully explain this to me. The reason I don't ask my professor is because this is a "bonus" problem and he won't explain it until later. Here are the exact instructions:

If you include time.h, you can get the number of seconds that have elapsed since Jan. 1, 1970 using time(NULL). Write a program that calculates the current date and time using this number. You cannot use any other functions other than time(NULL).

And after fixing the code from the link a bit, this is my final answer:

#include <time.h>
#include <stdio.h>

int main ()
{
  time_t seconds;

  seconds = time (NULL);
  printf ("%ld seconds since January 1, 1970");

  return 0;
}

I would greatly appreciate if someone would explain how this works. I've only worked with the iostream library, so that's why I'm so confused with these new commands. Thanks in advance.

[s10jam]

You want to know how that snippet of code works or how to convert that number to a current date and time?

[iLuvTofu]

Actually, I asked my professor if using <stdio.h> was OK and he said no, only <time.h> and <iostream>, so this code is not the right answer. If you could please explain to me how time(NULL) works, that would be great. He told me that I could use

int a = time(NULL)

to help me find the answer, and from there I could just figure it out. Thanks so much for your help, in advance. :D