Why does Date.yesterday counts as Date.today also?

Question

I have the following model and methods:

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

  def self.today
    where(:p         


        

Answer 1

This is happening because calculations.rb is calling the "current" method of the Date class for the configured timezone (Defaults to UTC).

If you open the rails console you can see the date at which "Date.yesterday" is calculating on by doing:

Time.zone.today

This will probably show you tomorrow's date. So Date.yesterday for what rails sees as today, is today. ;)

You can work with the Date library more directly by doing:

Date.today.advance(:days => -1)

This will give you yesterday's date like you expect whereas active_support is returning:

Date.current.advance(:days => -1) 

Answer 2

If you use the Time class, you'll have access to UTC (or "zulu") time zone rather than using the environment's time zone in Date class.

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

  def self.today
    where(purchase_date: today_utc_date)
  end

  def self.yesterday
    where(purchase_date: today_utc_date.yesterday)
  end

  private

  def today_utc_date
    @today ||= Time.zone.today
  end
end

Also, if you need to process an outside date, for example params[:purchase_date]:

Time.parse(params[:purchase_date]).utc.to_date