Running a function indefinitely at specific time of day in Python

I have a function that I need to run everyday from 5pm to 9am the next day, then starts again at 5pm. Below is my implementation:

import datetime as dt
import time 
while True:
    if dt.datetime.now().hour < 9 or dt.datetime.now().hour > 17:
        #some irrelevant function here
        print('Function processing')
        time.sleep(1) 
    else:
        print("Not time yet")
        time.sleep(1)
        continue

The above code works, but I would like to also execute a function once every first loop at 5pm and after the last loop at 9am. My first instinct is to do something like this:

def starting(): print("It's 9pm, time to start!")
def ending(): print("It's 5am, time to end")
while True:
    if dt.datetime.now().hour < 9 or dt.datetime.now().hour > 17:
        if #this is the first loop since 5pm:
            starting()
        elif #this is the last loop at 9am:
            ending()
        #some irrelevant function here
        print('Function processing')
        time.sleep(1)
    else:
        print("Not time yet")
        time.sleep(1)
        continue

I am not sure if this is the most optimal way of doing it, would appreciate some ideas.