y_lims = [0, 100]
fig, ax = plt.subplots()
ax.imshow(arr, extent=[x_lims[0], x_lims[1], y_lims[0], y_lims[1]], aspect=
    'auto')
ax.xaxis_date()
date_format = mdates.DateFormatter('%H:%M:%S')
ax.xaxis.set_major_formatter(date_format)
fig.autofmt_xdate()
plt.show()
Dates in the xaxis for a matplotlib plot with imshow