def split_date(df, date_col):
    """
    split YYYY-mm-dd date into year, month, day
    """
    list_date = df[date_col].tolist()
    list_year = [int(date[:4]) for date in list_date]
    list_month = [int(date[5:7]) for date in list_date]
    list_day = [int(date[8:]) for date in list_date]
    df["year"] = list_year
    df["month"] = list_month
    df["day"] = list_day
    return df