If in my case you work only over the years and do not want to add translations for each language with i18n just for choosing a year, you can add : locale => 'en' only for this date:
<%= f.date_select :start, :start_year => 1940, :end_year => Date.today.year, :discard_day => true, :discard_month => true, :locale => 'en' %>
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