How old are you?

I know.. it's none of my business, but sometimes you wonder, don't you, just how old you are in days? If this question consumes your waking hours, put the calculator away and crank up Excel.

Excel's Datedif function, while not documented, calculates the difference between two dates in a number of formats; days, months or years. The syntax of the function is: =datedif(start date,end date,units to return). The units must be provided by a quoted string in the format: "y" - full years, "m" - full months, "d" - full days, "md" - full days in excess of the last full month, "ym" - full months in excess of the last full year and "yd" - full days in excess of the last full year.

So, for example, this formula determines the number of days between the dates in cells B6 and C6: =DATEDIF(B6,C6,"d"). Type your birthday and today's day in the cells and you'll know immediately how old you are in days..