E21: =E20-E19+1 (The +1 includes both dates in the number, -1 would remove both dates) Eg, E19=01/01/2008 E20=31/12/2008 E21=365

There are a couple of ways to do this, one of which has already been shown (although incorrectly). Let's say that our dates are entered into A1 and A2. To show days from one date to another the best formula would be: = max( A1:A2) - min( A1:A2) This will ensure that you subtract the lower value from the higher, no matter how the dates are entered. And 'days between' should not be inclusive of another day, so there's no need for a +1 in the formula. But wait, there's more! =DATEDIF( MIN( A1:A2), MAX( A1:A2), "d") For this function to work, you need to have the Analysis ToolPak add-in activated (Tools / Add-ins, select from the list). This is a Microsoft add-in and safe to use. I don't know why it's not activated by default. This function allows you to show differences between dates in terms of days ("d" argument), months ("m" argument) or years ("y" argument) and is very helpful to avoid a lot of complicated date arithmetic. There is also a way to figure out the Work Days between dates, which can also be very useful. That is the =NETWORKDAYS() function, but I'll let you look that up in Excel's Help library, which describes its use pretty well.