According to documentation at http://guides.rubyonrails.org/i18n.html#adding-date-time-formats, the best way to ask for specific formats for a date is to define them in /config/
just want to clarify that if you use with active record, just simply convert the string datetime value to date object as example below.
datetime
date
en: date: formats: default: "%Y-%m-%d" short: "%b %d" long: "%B %d, %Y"
<%= l(post.the_created_at.to_date, format: :long) %>