gistfile1.rb

class Time

  def to_half_hour_start
    if self.min >= 30
      self.to_hour_end - 30.minutes
    else
      self.to_hour_start
    end
  end
  
  def to_half_hour_end
    if self.min >= 30
      self.to_hour_end
    else
      self.to_hour_end - 30.minutes
    end
  end

  def to_hour_start
    self.round - self.min.minutes - self.round.sec.seconds
  end
  
  def to_hour_end
    self.to_hour_start + 1.hour
  end

  def to_day_begin
    self.round - self.hour.hours - self.min.minutes - self.round.sec.seconds
  end
  
  def to_day_end
    self.to_day_begin + 1.day
  end
end