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delocalize provides localized date/time and number parsing functionality for Rails.


This gem requires the following versions:

  • Ruby >= 2.1.10 (Ruby >= 1.9.2 should work but isn't officially supported)
  • Rails >= 4.2 (earlier versions including probably even Rails 1 should work but aren't officially supported)

Check the Travis configuration in order to see which configurations we are testing.


You can use delocalize as a gem. Using delocalize as a Rails plugin has been discontinued and is no supported. If you want/need to use delocalize as a plugin (I really don't see a reason why you'd want to), consider using the 0-2-stable branch.

Rails 3 and above

To use delocalize, put the following gem requirement in your Gemfile:

gem "delocalize"

Rails 2

Note: Official support for Rails 2 has been discontinued. However, due to the way this gem has been rewritten for its 1.0.0 release, it should work with Rails 2 just fine. If you run into any problems, consider filing an issue.

To use delocalize, put the following gem requirement in your environment.rb:

config.gem "delocalize", :source => ''

In Rails 2.3, alternatively, you can use it with Bundler. See for instructions.

What does it do? And how do I use it?

Delocalize, just as the name suggest, does pretty much the opposite of localize.

In the grey past, if you want your users to be able to input localized data, such as dates and numbers, you had to manually override attribute accessors:

def price=(price)
  write_attribute(:price, price.gsub(',', '.'))

You also had to take care of proper formatting in forms on the frontend so people would see localized values in their forms.

Delocalize does most of this under the covers. All you need is a simple setup in your controllers and your regular translation data (as YAML or Ruby file) where you need Rails' standard translations.

Controller setup

The approach used in delocalize is based on Rails' own strong_parameters. In fact, if you are on Rails 3 with the strong_parameters gem installed or Rails 4 (which includes it by default), delocalize is mixed straight into the provided ActionController::Parameters class. Otherwise it uses its own similar class (Delocalize::Parameters).

You can then use delocalize as you would use strong_parameters:

class ProductsController < ApplicationController
  def create


  def product_params
    delocalize_config = { :released_on => :date, :available_until => :time, :price => :number }
    # with strong_parameters
    # without strong_parameters
    params.delocalize(:product => delocalize_config)[:product]
    # or


If you want to delocalize only certain parameters, configure those parameters and leave the others out – they will be kept as they are.


Delocalize doesn't automatically localize your data again (yet). There are various reasons for that but the main reasons are:

  • It's hard to do this properly with some amount of flexibility for you as the user of the gem without crazy hacks of Rails internals (a problem that delocalize previously suffered from).
  • Personally I feel that presentation logic (including forms) should be split out into separate objects (presenters, decorators, form objects and the like).

I might change my mind but as it stands but for the time being the gist is: Wherever you want to see localized values, you have to localize them yourself.


text_field :product, :released_on, :value => product.released_on ? l(product.released_on) : nil
text_field_tag 'product[price]', number_with_precision(product.price, :precision => 2)

You can of course use something like the Draper gem or the great Reform gem to wrap your actual object and override the relevant accessors.

Check out how this can be done in the demo app.

There's also a wiki page on how to write a custom input for SimpleForm.

Locale setup

In addition to your controller setup, you also need to configure your locale file(s). If you intend to use delocalize, you probably have a working locale file anyways. In this case, you only need to add two extra keys: date.input.formats and time.input.formats.

Assuming you want to use all of delocalize's parsers (date, time, number), the required keys are:

  • number.format.delimiter
  • number.format.separator
  • date.input.formats
  • time.input.formats
  • date.formats.SOME_FORMAT for all formats specified in date.input.formats
  • time.formats.SOME_FORMAT for all formats specified in time.input.formats
      separator: ','
      delimiter: '.'
      formats: [:default, :long, :short] # <- this and ...

      default: "%d.%m.%Y"
      short: "%e. %b"
      long: "%e. %B %Y"
      only_day: "%e"

    day_names: [Sonntag, Montag, Dienstag, Mittwoch, Donnerstag, Freitag, Samstag]
    abbr_day_names: [So, Mo, Di, Mi, Do, Fr, Sa]
    month_names: [~, Januar, Februar, März, April, Mai, Juni, Juli, August, September, Oktober, November, Dezember]
    abbr_month_names: [~, Jan, Feb, Mär, Apr, Mai, Jun, Jul, Aug, Sep, Okt, Nov, Dez]
    order: [ :day, :month, :year ]

      formats: [:long, :medium, :short, :default, :time] # <- ... this are the only non-standard keys
      default: "%A, %e. %B %Y, %H:%M Uhr"
      short: "%e. %B, %H:%M Uhr"
      long: "%A, %e. %B %Y, %H:%M Uhr"
      time: "%H:%M"

    am: "vormittags"
    pm: "nachmittags"

For dates and times, you have to define input formats which are taken from the actual formats. The important thing here is to define input formats sorted by descending complexity; in other words: the format which contains the most (preferably non-numeric) information should be first in the list because it can produce the most reliable match. Exception: If you think there most complex format is not the one that most users will input, you can put the most-used in front so you save unnecessary iterations.

Be careful with formats containing only numbers: It's very hard to produce reliable matches if you provide multiple strictly numeric formats!

Contributors and Copyright

Here is a list of all people who ever contributed to delocalize.

Copyright (c) 2009-2017 Clemens Kofler Released under the MIT license


Date/time and number parsing for Rails.







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