I don't think this is a bug, Ruby only parses English month names, it can't possibly try to check all languages in the world. When it can't deduce a month, it uses the current month, which right now is december.
AFAIK, Date.parse was NEVER intending to parse anything except English/American dates in English/American formats. Parsing dates internationally is waaaay harder than making dictionaries of month names: different cultures have different (often incompatible) date formats. Take a look at this list, for ex: https://en.wikipedia.org/wiki/Date_format_by_country
International date parser is a cool idea for standalone gem, but I don't think it could be ever expected to be in stdlib.
Even if Ruby have never intended to parse dates other than English it works quite well parsing Spanish dates. I'm quite confident that it uses dates_international.rb for the magic. I base my belief in the fact that Ruby and that code reproduce the exact same bug, buy defulting to the current month. The the problem is solved by changing line 37 from:
37: month_from = string[/[^\s\d,]+/i]
To:
37: month_from = string[/[a-z]+/i]
I extended the Date class locally to get pass the difficulty. Would like to contribute to the non English speaking Ruby community. Confirming that the suggested solution work for other languages as well and then merging to the main branch.
I would need to know exactly how the library is connected to Ruby in order to try. Help needed.
So is it a dates_international.rb's problem? Then sorry but the ruby's core do not ship that library. You might have obtained a copy of it from somewhere else. Do you remember where? Or, you might want to contact @jackrg directly. Let him know this issue and I hope he can fix it.