You can add custom date/time formats to your translation file. To see what time-based substitutions are possible, consult a reference for strfime
formats:
default: ! '%Y-%m-%d'
long: ! '%B %d, %Y'
short: ! '%b %d'
custom: ! '%A, %M %B, %Y @ %l:%M%P'
In your view, you'd make use as follows:
<%= l o.created_at, :format => :custom %>
You may need to get rid of blank entries in your en.yml file to correct your translation errors.