It was my client (Mail on OS X) that messed up font size and just saw it from the web browser..
This is the sort of ambiguity/inconsistency I was referring to. Intervals need a context in order to have a meaning but they never gave me issues except from leap years. So, I think it should be solved by “simply” threating leap years in a different way. Intervals are used to approach a human meaning of time measure, what we call “age”. Leap years should represent a specific exception IMHO.
Kind regards,
Pietro Pugni