time_t sec = time(NULL);
gives me the seconds since 1970.

It works with the system clock...
So maybe the system clock is not synchron on two computers...

Is there a way to get the seconds since 1970 WITHOUT the system clock, so that it is synchron on two computers?


No. But you could open a socket to another computer and ask it what time it is. Read this link

commented: What if the other PC isn't wearing a watch? +2
commented: Nice +19