Is abbreviation size guaranteed to be a valid approach in all locales?

[José Valim]

I am concerned that abbreviation_size is not a valid approach to providing abbreviations across all locales. Unfortunately, it is very hard to prove that this would be the case, so I believe abbreviated_month_names and abbreviated_week_names should be their own options (as in the original proposal).

[Gustavo]

it's hard to know, maybe it's better to have the options instead of abbreviation size.
even if it's not actually necessary it will at least give more control to the users