Unix Time is defined as the number of seconds that have elapsed since when?

Unix time is defined as the number of seconds that have elapsed since Midnight, January 1, 1970 because this specific moment in time was chosen as the starting point for several reasons. Firstly, it allowed for a positive integer representation of time, simplifying calculations and storage. Additionally, this date was before the widespread use of computers, ensuring compatibility with older systems and facilitating the transition to Unix time. Lastly, this particular epoch was culturally significant as it marked a new beginning, aligning with Unix's aim to be a fresh start in computer operating systems.