How to validate the date such that it is after today in Rails?

Your question is (almost) exactly answered in the Rails guides.

Here's the example code they give. This class validates that the date is in the past, while your question is how to validate that the date is in the future, but adapting it should be pretty easy:

class Invoice < ActiveRecord::Base  validate :expiration_date_cannot_be_in_the_past  def expiration_date_cannot_be_in_the_past    if expiration_date.present? && expiration_date < Date.today      errors.add(:expiration_date, "can't be in the past")    end  end    end

Here's the code to set up a custom validator:

#app/validators/not_in_past_validator.rbclass NotInPastValidator < ActiveModel::EachValidator  def validate_each(record, attribute, value)    if value.blank?      record.errors.add attribute, (options[:message] || "can't be blank")    elsif value <= Time.zone.today      record.errors.add attribute,                        (options[:message] || "can't be in the past")    end  endend

And in your model:

validates :signed_date, not_in_past: true

I took @dankohn answer, and updated to be I18n ready. I also removed the blank test, because that's not the responsibility of this validator, and can easily be enabled by adding presence: true to the validates call.

The updated class, now named in_future, which I think is nicer than not_in_past

class InFutureValidator < ActiveModel::EachValidator  def validate_each(record, attribute, value)    record.errors.add(attribute, (options[:message] || :in_future)) unless in_future?(value)  end  def in_future?(date)    date.present? && date > Time.zone.today  endend

Now add the in_future key to your localization file.

For all fields under errors.messages.in_future, e.g. for Dutch:

nl:  errors:    messages:      in_future: 'moet in de toekomst zijn'

Or per field under activerecord.errors.models.MODEL.attributes.FIELD.in_future, e.g. for the end_date in a Vacancy model in Dutch:

nl:  activerecord:    errors:      models:        vacancy:          attributes:            end_date:              in_future: 'moet in de toekomst zijn'