In financial calculations, the time duration is often important. Consider the following example:<\/p>\n
Calculate the duration from April 27, 1988 to March 16, 2016.<\/strong><\/p>\n Mathematically, the problem can be thought of as<\/p>\n March 16, 2016 – April 27, 1988.<\/p>\n The typical date format may not be the most convenient for such calculation.<\/p>\n Excel sees the calculation as follows:<\/p>\n 42445 – 32260<\/p>\n The number 42445 is Excel’s serial number for the date March 16, 2016; similarly, 32260 corresponds to April 27, 1988. The serial number of a date is the number of days from the turn of 1900 to, and including, that day. (Apparently, Excel in Macintosh starts the serial number from the turn of 1904.)<\/p>\n 42445 can be confirmed as the number of days up to, and including, March 16, 2016, since the turn of 1900:<\/p>\n 75×365 + 26×366 + 12×365 +3×366 + 31 + 29 + 16 = 42445<\/p>\n To continue with the example above:<\/p>\n March 16, 2016 – April 27, 1988 = 42445 – 32260 = 10185 days<\/p>\n The corresponding number of years is 10185\/365 = 27.9.<\/p>\n Excel has built-in formulas for converting dates. I’ll be discussing some of them in future posts:)<\/p>\n