ActiveRecord with different Date/Time format

I have an application where user sets his/her preferred date/time
format. User is expected to enter datetime in his preferred format
across the application. Now the problem is for few formats the datetime
is parsed wrongly while create/update ActiveRecord.

For example user has set date/time format in hh:mm dd/MM/yyyy. Now if
user enters 17:00 04/05/2012 it parses it as 5 PM 5 Apr, 2012 where it
should be 5 PM 4 May, 2012

1.8.7 :004 > a = Article.create!(:name => 'a1', :published_at => '17:00
04/05/2012')
=> #<Article id: 2, name: "a1", published_at: "2012-04-05 17:00:00",
created_at: "2012-04-16 13:54:36", updated_at: "2012-04-16 13:54:36">

I understand that ruby/rails has predefined set of formats against which
the date/time string is evaluated and if matches any format in sequence
it parses given string with that format/

1.8.7 :006 > a = Article.create!(:name => 'a1', :published_at => '17:00
15/12/2012')
=> #<Article id: 4, name: "a1", published_at: nil, created_at:
"2012-04-16 13:55:43", updated_at: "2012-04-16 13:55:43">

Here user entered 15 December, 2012 which was parsed to nil. I
understand that ruby/rails was not able to match any predefined format
and hence returns nil.

Someone has already asked similar questions
(http://stackoverflow.com/q/2529990 and
http://www.ruby-forum.com/topic/57923) but the solution seems not
applicable in my case as I don't want single datetime format across the
application as each user will have his own preferred datetime format.

Now to work with multiple datetime format, we are planning to manipulate
it before the params is passed to the ActiveRecord. So the steps would
like

1. Read datetime from params map
2. Parse it with user's preferred datetime format
3. Format datetime to the default format used by ActiveRecord
4. Replace current datetime in params with re-formatted datetime
Here is a snippet of the controller

class ArticlesController < ApplicationController
  before_filter :format_date_time, :only => [:create, :update]
  ...
  ...
  private
    def format_date_time
      datetime = params[:datetime]
      params[:datetime] = DateTime.strptime(datetime,
pref_date_time_format).strftime('%c')
    end
end

Would anyone please verify if it is right approach or not? Also I would
appreciate someone outlines better ways to accomplish this.

Thanks,
Amit Patel

Since each user inputs a data with different formats, you have to
treat them as they come in to the controller.

Using strptime with the specified format is the correct way to create
the correct datetime give the user's format.
When showing this same date you'll present them in the format they
use, but the date on the database is always
going to be in the same format.

You could also override the setter of the datetime param on the model,
but I've never had good experiences
overriding attributes in AR.

When showing the date you can use a decorator to format it on the view
using the I18n.localize with :format parameter.

Thanks Draiken, for your valuable inputs.

Actually the application is not internationalized fully. We just have
given liberty to user to choose different date/time formats. So we would
not be using I18n for now.

I also feel not to override attribute setter in AR to manipulate
date/time before saving.

It looks ok to me apart from the fact that you need to allow for the
user entering invalid data so that strptime fails. I suggest you have
a look at datetime_select however, you might find that useful and then
you don't have to worry so much about operator error.

Colin

Thanks Colin. We have used datetime_select in our application.

Do you mean you have changed to using datetime_select, or you are
already using datetime_select and have the problem you previously
described?

Colin

Hi Colin,

We are using datetime_select but planning to use javascript datetime
picker. We chosen
http://jongsma.org/software/protoplasm/control/datepicker which also
support configurable datetime format. So we are facing this issue while
preparing POC.

Thanks,
Amit