RAILS: undefined method `map' caused by missing I18n translation - ruby-on-rails

Question

I changed the format for a datetime field in a RAILS 4 new.html.erb from :string to datetime and it caused error as below:
undefined method `map' for "translation missing: zh-CN.date.order":String
The view code causing the error above is:
<%= f.input :start_time, :label => t("Start Time"), required: true, :as => :datetime, :ampm => true, :minute_step => 10, :start_year => Date.today.year - 1, :end_year => Date.today.year + 1, :format => 'YYYY/MM/DD/HH/MM', :use_month_numbers => true, :include_blank => true %>
The RAILS source code blows up is in actionview/helpers/date_helper.rb:
def translated_date_order
date_order = I18n.translate(:'date.order', :locale => #options[:locale], :default => [])
date_order = date_order.map { |element| element.to_sym } #<<<<<<===blows up
forbidden_elements = date_order - [:year, :month, :day]
if forbidden_elements.any?
raise StandardError,
"#{#options[:locale]}.date.order only accepts :year, :month and :day"
end
date_order
end
I do have a file zh-CN.yml under /config/locale/ and it is providing translations for others except this one.
UPDATE portion of zh-CN.yml:
zh-CN:
#maint_recordx
Mfg Batches : '订单批次一览'
New Batch : '新批次'
Update Batch : '更新批次'
Edit Batch : '更新批次'
...........

Answer 1

After being bitten by this same error, I found that Rails sets the following key:
:'date.order'
to the value:
["year", "month", "day"]
for the default :en locale
You can confirm this by running the following snippet in rails console for a default rails install:
date_order = I18n.translate(:'date.order', :locale => :en, :default => [])
Notice I just switched #options[:locale] for the default :en value
The rails helper you reference, expects an array for the date_order value, and will blow up if it doesn't get one.
In my case, I improperly configured the I18n::Backend::ActiveRecord gem and therefore it interfered with the value being returned by I18n. You probably have a similar issue preventing the correct value for the :'date.order' key being returned.
EDIT:
In order to fix this, you should probably just need to install the gem 'rails-i18n'. It will handle returning the correct date formats for supported locales. In my case I had a custom configuration in my es.yml locale file that returned an incorrect date format.

Answer 2

Bingo !!! You just have to add the missing key translation to your local translations.
I solved it by adding
en:
date:
order: ["day", "month", "year"]
to
config/locales/en.yml