Rails: getting nil values in hidden field -

i'm getting nil values when i'm using hidden field

<%= form_for @hour |f| %>   <%= f.hidden_field "days[]", :value => "sunday" %>   <%= f.hidden_field "days[]", :value => "monday" %>   <%= f.hidden_field "days[]", :value => "tuesday" %>   <%= f.hidden_field "days[]", :value => "wednesday" %>   <%= f.hidden_field "days[]", :value => "thursday" %>   <%= f.hidden_field "days[]", :value => "friday" %>   <%= f.hidden_field "days[]", :value => "saturday" %> <% end %> 

my parameters:

"days"=>[nil,nil,nil,nil,nil,nil,nil] 

am doing hidden fields wrong?

thanks

check if below code helps.

<%= form_for @hour |f| %>   <%= f.hidden_field "days[0]", :value => "sunday" %>   <%= f.hidden_field "days[1]", :value => "monday" %>   <%= f.hidden_field "days[2]", :value => "tuesday" %>   <%= f.hidden_field "days[3]", :value => "wednesday" %>   <%= f.hidden_field "days[4]", :value => "thursday" %>   <%= f.hidden_field "days[5]", :value => "friday" %>   <%= f.hidden_field "days[6]", :value => "saturday" %> <% end %> 

params:

  parameters: {"utf8"=>"√",authenticity_token"=>"m84ly0ok8nwkzqv2zgzvtp1trosz3m0oll7w5w5pk+i=",  "hour"=>{"days"=>{"0"=>"sunday", "1"=>"monday", "2"=>"tuesday",  "3"=>"wednesday", "4"=>"thursday", "5"=>"friday", "6"=>"saturday"}}, "commit"=>"create hour "} 

updated
dynamic :

<%= form_for @hour |f| %>  <%= f.hidden_field "days][", :value => "sunday" %>  <%= f.hidden_field "days][", :value => "monday" %>  <%= f.hidden_field "days][", :value => "tuesday" %>  <%= f.hidden_field "days][", :value => "wednesday" %>  <%= f.hidden_field "days][", :value => "thursday" %>  <%= f.hidden_field "days][", :value => "friday" %>  <%= f.hidden_field "days][", :value => "saturday" %> <% end %> 

output:

   parameters: {"utf8"=>"√",  "authenticity_token"=>"jxcdmsokjclxu4ysswp/gw19ejy4ty3nwdbw/l/+lru=", "user"=>{"hour"=>["sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday"]}, "commit"=>"create hour"}