def get_time_string(hour):
    """Returns a string to display given a value 8-22 (8am to 10pm)"""
    if hour < 12:
        return str(hour) + ":00am"
    elif hour == 12: 
        return str(hour) + ":00pm"
    elif hour > 12 and hour < 23:
        return str(hour-12) + ":00pm"
    else:
         return None