[homingbrain]

However, since only one age value can be actually correct in this case, the use of logic looks less like a feature of the programmer's mind and more like a bug.

[mikeash]

One of them is a case of GIGO, using "36 years ago" as input when the correct value is 35. Fixing that reduces it to two values, and the discrepancy is down to day versus year granularity.

[TeMPOraL]

All three results are close to each other and to the true value, so I'd still call it a feature :).