In Stata, I need to calculate the age of a patient at the last check-up by using the date of birth and the check-up date. All the data is inputted via spreadsheet. The dates in the spreadsheet are formatted like this: 6/12/57, 8/1/08, etc. I am unsure on how to convert the string to an integer for subtraction and not sure on how to correctly write the dates (or how to change all the dates to fit the format). I have a large data set so it would seem impractical to individually change each date.