The EDATE function is fully automatic. Simply supply a valid date and a number of months and EDATE will return a new date. To subtract months from a date, supply a negative value.
To move forwards and backwards in years from a certain date, you can multiply by 12 inside EDATE like this:
=EDATE(A1,12*10) // 10 years =EDATE(A1,12*50) // 50 years