安装后
$ rails generate validates_timeliness:install
会生成 initializer 和 locale 配置文件！
使用例子：
validates_datetime :occurred_atvalidates_date :date_of_birth, :before => lambda { 18.years.ago }, :before_message => "must be at least 18 years old"validates_datetime :finish_time, :after => :start_time # Method symbolvalidates_date :booked_at, :on => :create, :on_or_after => :today # See Restriction Shorthand.validates_time :booked_at, :between => ['9.00am', '5:00pm']validates_time :breakfast_time, :on_or_after => '6:00am', :on_or_after_message => 'must be after opening time', :before => :lunchtime, :before_message => 'must be before lunch time' 如何使用？
class Person < ActiveRecord::Base validates_date :date_of_birth, :on_or_before => lambda { Date.current } # or validates :date_of_birth, :timeliness => {:on_or_before => lambda { Date.current }, :type => :date}end# or even on a specific record, per ActiveModel API.@person.validates_date :date_of_birth, :on_or_before => lambda { Date.current } 其实和平常的‘校验’也没什么两样，只是我们对 日期／时间的校验 不常用罢了。如下：
validates_date - validate value as datevalidates_time - validate value as time only i.e. '12:20pm'validates_datetime - validate value as a full date and timevalidates - use the :timeliness key and set the type in the hash.
对于上面的 validates 方法，我们可以有如下选项：
:is_at - Attribute must be equal to value to be valid:before - Attribute must be before this value to be valid:on_or_before - Attribute must be equal to or before this value to be valid:after - Attribute must be after this value to be valid:on_or_after - Attribute must be equal to or after this value to be valid:between - Attribute must be between the values to be valid. Range or Array of 2 values.
:allow_nil - Allow a nil value to be valid:allow_blank - Allows a nil or empty string value to be valid:if - Execute validation when :if evaluates true:unless - Execute validation when :unless evaluates false:on - Specify validation context e.g :save, :create or :update. Default is :save.
:ignore_usec - Ignores microsecond value on datetime restrictions:format - Limit validation to a single format for special cases. Requires plugin parser.