#pseudo code does not work
    today = datetime.datetime.today()
    try:
        #convert df column to datetime column
        expdate = pd.to_datetime(
            df[' "Date Out of  Service"'])
    except ValueError:
        # quick fix to deal with the fact that some columns don't have a date.
        # This ridiculous value will be easy to tease out of finaldataset
        expdate = datetime.datetime(1970, 1, 1)
    df['Days til OOS'] = (expdate - today).days
    return (df['Days til OOS'])