Since each date is really just a number stored in Excel, to compute the midpoint of two dates you would use the same mathematical formulas you would use to calculate the midpoint of two numbers ...

Microsoft Word has a date field, but it's not easy to use in an expression. If you need to update dates in a document, use Excel to calculate the dates and then run a mail merge.

One of the many features of Excel is being nosy. That's right, you can quickly calculate a persons age as long as you have their birth date.