Date Calculation

I want to calculate the Dates.  I have a column that is in the DateTime format.  I want to create a new column that shows me the number of years old a building is from the start date until present (i,e, today's date).  For example, I want to take 2006-10-28 and figure out how old building is today 2016-10-28.   What's the best approach?

Thanks,

Derreck