This online calculator was created at a user's request. The user had written something along the lines of: "I'd like to be able to find out the resulting date after adding a specified number of days to a specified date. For example, wedding day + 5,000 days, or birthday + 13,000 days."
So, I've created such a calculator. Just enter the date, the number of days to add/subtract and you will get the result.