SAS regards a date as the number of days since January 1, 1960. (Why? It's a closely guarded secret. It was probably some SAS programmer's kid's birthday or something like that.) Days before January 1, 1960 are stored as negative integers, and SAS automatically compensates for leap years. This way of storing dates is actually quite useful, since finding the time elapsed between two dates requires only subtracting two numbers. Likewise, times of day are stored as the number of seconds past midnight. SAS can print the dates and times in more recognizable ways with FORMAT statements; these will be described later.