trying to set days within current month

day = Time.current.day
    day_to_use = day - 1
    month = Time.current.month
    #sets number of days within current month
    if month == 4 || 6 || 9 || 11
      days_within_month = 30
    elsif month == 1 || 3 || 5 || 7 || 8 || 10 || 12
      days_within_month = 31
    else
      days_within_month = 28
    end