How do I change the format ActiveRecord expects when parsing dates from a text field in a form? - ruby-on-rails-3

Question

The problem
I have a Ruby on Rails model with a Date attribute.
In the form for this model, I am using a single text field with a JQuery datepicker to represent this attribute (not a drop down for each of year, month, and day, as is the Rails custom).
The datepicker inserts dates with a mm/dd/yyyy format.
Rails is expecting dates with a dd/mm/yyyy format.
Examples
If a user selects March 12th, 2012, the datepicker puts 03/12/2012, which is interpreted by Rails as December 3rd, 2012.
If a user selects March 20th, 2012, the datepicker puts 03/20/2012, which is interpreted by Rails as the 3rd day of the 20th month of 2012. Since this date doesn't exist, Rails casts this to a nil value (I think).
Question
How do I change the date format Rails uses when parsing this date text field?
Notes:
1) I do not want to change the format of the date the datepicker inserts into the text field,
2) I am not asking about displaying my date attribute in a view.

Answer 1

I initially thought this could be solved through the Rails internationalization features, but it turns out I was wrong.
Ever since Ruby 1.9, the standard format for date parsing is dd/mm/yyyy, so as to better accomodate international users. More details can be found in this SO answer.
That standard is maintained in Rails, as Date.parse is now used to process data from form inputs. Using a before_validation callback won't work because the field is going to be received as nil by the callback method.
Right now there are two gems dealing with this specific issue, namely that date parsing in Rails does not follow the locale settings from I18n.locale. Both seem to work well.
delocalize, by clemens - Seems to have been applied successfully in a decent number or projects and has the highest number of stars at the moment.
i18n_alchemy by carlosantoniodasilva - This one has been released more recently. The author is a Rails core team member, and a very active one at that. Definitely deserves a look.

Answer 2

Since you don't want to change the picker's format, I would suggest you use a hidden field for the actual model property.
For example, add a hidden field for the model's date property, assuming you use a form builder as usual:
f.hidden_field :date
Then for the picker text input, don't bind it to the model's date property. Let's say the hidden field has ID 'modelname_date' and the picker text input has ID 'date_picker', use the following to make it work:
$(function(){
$("#date_picker").datepicker({altField: '#nodelname_date', altFormat: 'dd/mm/yyyy'});
});
In this way the date picker shows the date as 'mm/dd/yyyy' but Rails will see the date as 'dd/mm/yyyy'.
Update:
If you want to work this out on the Rails side, here's another solution I'd suggest:
Add a virtual property to your model: attr_accessor :bad_format_date
Add a before_validation callback in which you parse the input date and assign it to the real field:
before_validation do
self.date = Date.strptime(bad_format_date, "%m/%d/%Y")
end
Then for the form on the view use bad_format_date but initialize it with the date field value (if it's an edit form).

Answer 3

The timeliness gem makes ruby date/time parsing much more customizeable and integrates well with Rails.
Since you're working with Rails, be sure to check out the validates_timeliness project as well by the same guy. It includes all of timeliness plus sophisticated date/time validation methods for ActiveModel.

Answer 4

You could try do something like this.
$(function(){
$('#date_picker').datepicker( {
beforeShowDay: $.datepicker.noWeekends,
showOtherMonths: true,
selectOtherMonths: true,
dateFormat: 'dd-mm-yy',
defaultDate: date,
gotoCurrent: true
});

Answer 5

I just add the following monkey patch to config/time_formats.rb
class Date
class << self
alias :euro_parse :_parse
def _parse(str,comp=false)
str = str.to_s.strip
if str == ''
{}
elsif str =~ /^(\d{1,2})[-\/](\d{1,2})[-\/](\d{2,4})/
year,month,day = $3.to_i,$1,$2
date,*rest = str.split(' ')
year += (year < 35 ? 2000 : 1900) if year < 100
euro_parse("#{year}-#{month}-#{day} #{rest.join(' ')}",comp)
else
euro_parse(str,comp)
end
end
end
end