matplotlib how to specify time locator's start-ticking timestamp?

Question

All I want is quite straight forward, I just want the locator ticks to start at a specified timestamp:
peudo code: locator.set_start_ticking_at( datetime_dummy )

Answer 1

Instead of using the interval keyword parameter, use bysecond and byminute to specify exactly which seconds and minutes you with to mark. The bysecond and byminute parameters are used to construct a dateutil rrule. The rrule generates datetimes which match certain specified patterns (or, one might say, "rules").

For example, bysecond=[20, 40] limits the datetimes to those whose seconds equal 20 or 40. Thus, below, the minor tick marks only appear for datetimes whose soconds equal 20 or 40.

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.dates as matdates

N = 100

fig, ax = plt.subplots()
x = np.arange(N).astype('