Translate month name

I have translations downloaded from
https://github.com/svenfuchs/rails-i18n
Things like I18n.l(Time.now, :format => :long) works fine. It returns
'30 août 2011' for example if I set I18n.locale = :fr.

My problem is as follows. I have a date with a french month name like
'30 août 2011'. '30 août 2011'.to_time does not work.
I have to translate 'août' to english first using the en.yml file (I
have a translation 'août: aug' in it), so I get '30 aug 2011'. '30 aug
2011'.to_time works just fine.
In this way I can solve my own problem, but it looks ugly to me to
create a translation 'août: aug' in the en.yml file while I already have
the right month names in the fr.yml file.

Anyone who knows a better solution?