how to plot time on y-axis in '%H:%M' format in matplotlib?

Question

i would like to plot the times from a datetime64 series, where the y-axis is formatted as \'%H:%M, showing only 00:00, 01:00, 02:00, etc.

this is what the plot look

Answer 1

For that to work you need to pass datetime objects (and I mean datetime, not datetime64). You can convert all timestamps to the same date and then use .tolist() to get the actual datetime objects.

y = df['a'].apply(lambda x: x.replace(year=1967, month=6, day=25)).tolist()
ax = plt.subplot()
ax.plot(df.index, y)
ax.yaxis.set_major_locator(HourLocator())
ax.yaxis.set_major_formatter(DateFormatter('%H:%M'))