code: def day_postfix(day):
      
  
      if day != 11 and day % 10 == 1:
          postfix = "st"
      elif day != 12 and day % 10 == 2:
          postfix = "nd"
      elif day != 13 and day % 10 == 3:
          postfix = "rd"
      else:
          postfix = "th"
  
      return postfix
docs: Returns day's correct postfix (2nd, 3rd, 61st, etc).