相关疑难解决方法(0)

我有以下模型和方法:

class UserPrice < ActiveRecord::Base
  attr_accessible :price,  :purchase_date,    

  def self.today
    where(:purchase_date => Date.today)
  end

  def self.yesterday
    where(:purchase_date => Date.yesterday)
  end

为什么在我的表格上,如果我给我的date_select字段1/4/2012 :purchase_date(yesterday方法)它也算作今天(today方法),如果我给它1/5/2012(今天)它是零？

PS我正在使用Rails 3.0.10和PostgreSQL.

更新

这是我的控制台返回:

$ rails console --s
Loading development environment in sandbox (Rails 3.0.10)
Any modifications you make will be rolled back on exit
irb(main):001:0> Date.today
=> Wed, 04 Jan 2012
irb(main):002:0> Time.now
=> 2012-01-04 21:28:07 -0500
irb(main):003:0> Time.zone.now
=> Thu, 05 Jan 2012 02:28:18 UTC +00:00
irb(main):004:0> Date.yesterday
=> Wed, …