Leap years cannot be programmed easily. There is a leap year every four years, but not if it is a even 100 year. But then again; it is leap year if it is an even 400 years. There was leap years at 1996, 2000 and 2004, but at the turn of next century there will be leap years 2096 and then 2104 (common year 2100)

This cannot easily be "programmed" into a mechanical clock and my guess is that it is not worth doing it in a digital. So they go with the easier algorithm; there are no leap years (actually 28:th of Feb always is followed by 1:st of March).

So every time there is a 29:th of February (always a Tuesday btw) your Aerospace will display 1:st of March and you need to correct it (twice).

Hope I got it right, it's easier to express in program code

Just checked up the words that was used on the Breitling web. It says:

Calendar: Digital, day and date programmed for 4 years

Maybe they mean: programmed for 4 years rule, but not 100 and 400 years rule? and the Aerospace actually does keep track of the 29:th?

It doesn't.

I'm sure you're right, but it makes very little sense imo. It should be much simpler doing more advanced algorithms with electronics than with mechanics. Otherwise we would celebrate Charles Babbage rather than Alan Turing

What Breitling models are automatic perpetuals?