start date and start time of a process - jiffies
 

In /proc/<process number>/stat is a field, which corresponds to the numbers of jiffies (since boot up) at process start time. Does anybody know the exact relationship of jiffies and seconds? From this it would be possible to calculate the start date and start time of a process (using additionally the time since boot up and the actual date and time). Or is there an easier way to access the process start date and start time? I would like to use these data in a bash script.

Some more problems: jiffies may wrap around. Is it possible to detect, if wrap around has occured?