In Chapter 24, Adding Timing Controls to Scripts, you got a brief introduction to the
current date command in the Standard Additions scripting addition and the
date command of the UNIX shell. Here, we’ll show you how to use date and time arithmetic and to compare dates to make better use of your time.
Knowing what day and time it is right now is only the beginning. You often have a second date, and you want to know how much time has passed since then or how much time will pass until then. For example, given your birthday, how old are you right now? Given the deadline for your next term paper, how much time do ...