On Sat, Jun 26, 2021 at 01:13:06PM +0200, Bal??zs K??si wrote:
> Ken's solution can be fixed for non-leap years by using <= instead of <,
> but it breaks down for leap years. e.g.
> 
> a := Date year: 2003 month: 3 day: 1.
> b := Date year: 2004 month: 2 day: 29.
> 
> b year - a year - (a dayOfYear <= b dayOfYear ifTrue: 0 ifFalse: 1) "
> outputs 1 "
> 
> What seems to work is to let Date handle the leap year case with
> #addMonths:. e.g.
> 
> yd := b year - a year.
> (a addMonths: 12 * yd) > b ifTrue: [ yd - 1 ] ifFalse: [ yd ]. " outputs 0 "
> Bal??zs
>

Here is another variation that seems to work with leap years:
 

Date ageAt: aDate
	"Given a date representing a person's birthday, answer that person's age at
	 aDate as reported in the Western tradition. Note that age is reported differently
	in India and possibly other cultures."

	" '9 Aug 1984' asDate ageAt: Date today "

	^ (aDate monthIndex > self monthIndex
			or: [aDate monthIndex = self monthIndex and: [aDate dayOfMonth >= self dayOfMonth]])
		ifTrue: [aDate year - self year]
		ifFalse: [aDate year - self year - 1].


It's a bit discouraging when I use this with my real birthday though ;-)

Dave