The function time() retrieves the current calendar time from the system's clock. It has the following prototype:
time_t time(time_t * tp);
In systems in which no clock is available, the function returns -1.
I found this on the internet. I have a question about the above quote where they mention there could be situation in which "no clock is available".
What do they mean by no clock availabe? For example I am running linux, doesn't all OS have some kind of clock?
I need to add some time interval to the current time, how I do this?