Calculating Age

Both ‘first’ and ‘second’ need to be date vectors. This is to achieve a calculation of age rounded DOWN in the same way that we say our age (as in we say 17, right up until the day we turn 18). round(x,0) will round up, floor(x) will also cause issues, if the two dates are the same day of the same month but on different years.

EDIT: This had an error and has been superseded by this post.