If you just want to plot the dates with their related values

    dates = ['2015-03-12','2015-03-12', '2015-03-20','2015-03-20']
    values = [80, 55, 1, 100]
    dates = pd.to_datetime(dates)
    dates_str = dates.strftime('%Y-%m-%d')
    plt.scatter(dates_str, values)