This is happening on my Rails 4.0.3 app but seems to also be present in master.
There seems to be a discrepancy between the :long format defined in Date::DATE_FORMATS (%B %e, %Y) and the one defined in the default locale/en.yml (%B %d, %Y).
%B %e, %Y
%B %d, %Y
Namely, the %e parameter in the former causes the rendered date to have two spaces between the month and the day when the day is single-digit, due to the fact that it pads the day number with spaces. The latter instead pads the day number with zeroes.
Is this discrepancy known of? I discovered it today while testing, because I used to_s(:long) in my test and the l helper in my view.
In my opinion, the date should be displayed without leading zeros on the day but also without repeated spaces. A format string of %B %-e, %Y seems to accomplish this.
%B %-e, %Y
Hey Gabriele! I've also been able to reproduce and using your format string suggestion really seems to fix it. (: I'll make a PR soon.