Chapter 15. Formatting and calculating date and time
YOU CAN use date and time values to stamp documents and to perform date and time arithmetic. Creating a production schedule or a monthly billing system is relatively easy with Microsoft Excel. Although Excel uses numeric values to count each nanosecond, starting from the beginning of the twentieth century, you can use formatting to display those numbers in whatever form you want.
Understanding how Excel records dates and times
Excel assigns serial values to days, hours, minutes, and seconds, which makes it possible for you to perform sophisticated date and time arithmetic. ...