ruby script/plugin install http://svn.viney.net.nz/things/rails/plugins/validates_date_time/

The validators can be used to parse strings into Date and Time objects as well as restrict an attribute based on other dates or times.

  class Person < ActiveRecord::Base
    validates_date     :date_of_birth
    validates_time     :time_of_birth
    validates_date_time :date_and_time_of_birth
  end

Use :allow_nil to allow the value to be blank.

  class Person < ActiveRecord::Base
    validates_date :date_of_birth, :allow_nil => true
  end

== Supported formats

The default for the plugin is to expect dates in day/month/year format. If you are in the US, you will want to change the default to month/day/year by placing the following in config/environment.rb

  ActiveRecord::Validations::DateTime.us_date_format = true

Date format examples:

* 2006-01-01
# 1 Jan 06
# 1 Jan 2006
# 10/1/06
# 1/1/2006

Time format examples:

# 1pm
# 10:11
# 12:30pm
# 8am

Datetime format examples:

* 1 Jan 2006 2pm
# 31/1/06 8:30am

== Examples

If an attribute value can not be parsed correctly, an error is added:

  p = Person.new
  p.date_of_birth = "1 Jan 2006"
  p.time_of_birth = "5am"
  p.save # true
  
  p.date_of_birth = "30 Feb 2006"
  p.save # false, 30 feb is invalid for obvious reasons
   
  p.date_of_birth = "java is better than ruby"
  p.save # false

In the final example, as I'm sure you are aware, the record failed to save not only because "java is better than ruby" is an invalid date, but more importantly, because the statement is blatantly false. ;)

=== Restricting date and time ranges

Using the :before and :after options you can restrict a date or time value based on other attribute values and predefined values. You can pass as many value to :before or :after as you like.

  class Person
    validates_date :date_of_birth, :before => [:date_of_death, Proc.new { 1.day.from_now_to_date}], :after => '1 Jan 1900'
    validates_date :date_of_death, :before => Proc.new { 1.day.from_now.to_date }
  end
  
  p = Person.new
  p.date_of_birth = '1800-01-01'
  p.save  # false
  p.errors[:date_of_birth] # must be after 1 Jan 1900
  
  p.date_of_death = Date.new(2010, 1, 1)
  p.save  # false
  p.errors[:date_of_death] # must be before 
  
  p.date_of_birth = '1960-03-02'
  p.date_of_death = '2003-06-07'
  p.save  # true

You can customise the error messages for dates or times that fall outside the required range. The boundary date will be substituted in for %s. Eg:

  class Person
    validates_date :date_of_birth, :after => Date.new(1900, 1, 1), :before => Proc.new { 1.day.from_now.to_date }, :before_message => 'Ensure it is before %s', :after_message => 'Ensure it is before %s'
  end

There is currently no advanced documentation for this plugin.