the problem is the following line:

actionpack/lib/action_view/helpers/form_helper.rb @ 870

self.field_helpers = (FormHelper.instance_methods - ['form_for'])

one possible fix is:

self.field_helpers = (FormHelper.instance_methods - ['form_for']) +
        (DateHelper.instance_methods - ["distance_of_time_in_words", "select_month", "select_second", "select_datetime", "distance_of_time_in_words_to_now", "select_day", "select_time", "time_ago_in_words", "select_hour", "select_date", "select_year", "select_minute"]) +
        (FormOptionsHelper.instance_methods - ["options_for_select", "option_groups_from_collection_for_select", "grouped_options_for_select", "options_from_collection_for_select", "time_zone_options_for_select"])