Who can do an action at a specific time?

I'm using the following countdown code. And I don't know how to do an action at a specific given time. For example I want to print hello at 01:59:45.

The code below:

I've tried I'd time2= '01:59:45' but is not working.

#!/usr/bin/python

from Tkinter import *
import time

rootWindow = Tk()
rootWindow.title('Tk Timer')
rootWindow.geometry("300x250")
rootWindow.resizable(0,0)

defaultColour = rootWindow.cget("bg")

time1 = ''
prevSec = ''
mins = 0
secs = 0
hours = 2
running = False
#clock = Label(rootWindow, font=('fixed', 20, 'bold'))
clock = Label(rootWindow, font=('fixed', 20))
clock.grid(row = 1, column = 2, padx = 5, pady = (5,2))

def tick():
global prevSec, time1, secs, mins, hours, running
# get the current local time from the PC
#    time2 = time.strftime('%Y/%m/%d %H:%M:%S')
if running:
    newSec = time.strftime('%S')
else:
    newSec = ''
    prevSec = ''
if newSec != prevSec:
    prevSec = newSec
    secs = secs - 1
    if secs < 0:
        secs = 59
        mins = mins - 1
        if mins < 0:
            mins = 59
            hours = hours - 1
            if hours < 0: 
                hours = 0
                mins = 0
                secs = 0
                clock.config(bg='dark red')
time2 = '%02d:%02d:%02d' % (hours, mins, secs)
# if time string has changed, update it
if time2 != time1:
    time1 = time2
    clock.config(text=time2)
# calls itself every 200 milliseconds
# to update the time display as needed
# could use >200 ms, but display gets jerky
clock.after(200, tick)

tick()

def start_btn():
    global running
    clock.config(bg='green')



btn_start.config(state='disabled',background=defaultColour)
btn_stop.config(state='normal',bg='dark red')
btn_reset.config(state='disabled')
running = True

def stop_btn():
global running 
clock.config(bg='dark red')
btn_start.config(state='normal',bg='green')
btn_stop.config(state='disabled',bg=defaultColour)
btn_reset.config(state='normal')
running = False

def reset_btn():
global prevSec, time1, secs, mins, hours, running 
clock.config(bg=defaultColour)
hours = 2
mins = 0
secs = 0
prevSec = ''
time1 = ''
running = False
btn_stop.config(state='disabled',bg=defaultColour)
btn_start.config(state='normal',bg='green')
btn_reset.config(state='disabled')

btn_reset = Button(rootWindow, state='disabled', text = 'Reset', command = reset_btn)
btn_reset.grid(sticky=EW, row = 1, column = 3, padx = 5, pady = (5,2))
btn_start = Button(rootWindow, text = 'Start', bg='green', command = start_btn)
btn_start.grid(sticky=EW, row = 2, column = 3, padx = 5, pady = 2)
btn_stop = Button(rootWindow, state='disabled', text = 'Stop', command = stop_btn)
btn_stop.grid(sticky=EW, row = 3, column = 3, padx = 5, pady = (2,5))
btn_exit = Button(rootWindow, text = 'exit', command = exit)
btn_exit.grid(row = 4, column = 1, padx = 5, pady = 5) 

rootWindow.mainloop()

So I would like at a specific time do make an action. Like printing a message blinking a LED etc.