I have a training spreadsheet in excel. I would like to know how to highlight a date if the dates has expired one year from today's date. Is there a way to do that?

You can use "Conditional Formatting" to highlight the cell based on a given condition. Conditional Formatting is found under the Format menu.

The Condtion you would want would be something like:

Today() > A1+365

Also make sure that the Condition 1 box says "Formula is" and you will need a "=" before the formula begins, so excel does not treat your formula as a string!