fig = plt.figure()
ax = fig.gca()
s.plot(ax=ax)
i = 0
ax.text(s.index[i], s.iloc[i], 'Hello')
ax.text(dt.date(2014, 11, 9), 500, 'World')
ax.text(Timestamp('2014-11-10'), 777, '!!!')
plt.show()
Matplotlib, settng in-plot text with plt.text() with pandas time series data