[Tkinter] How to adjust time - tkinter

[Ondrej]

Hello everbody,

please help me to solve one issue with my tkinter clock. Time is imported from my cpu but sometimes I need to shift few seconds down or up, so I created buttons with command functions, the problem is that i don´t know how to set the def or those buttons properly (with print function, or transfor string to int and back?), Thanks for any advice. Bellow you can see code:

import sys, random
from tkinter import *
from tkinter import ttk

import time

 
def tick():
    time_string=time.strftime('%H:%M:%S')
    clock.config(text=time_string)
    clock.after(200,tick)
    
root=Tk()

def callback():
    time_string=time.strftime(chr('%H:%M:%S'))

button1=ttk.Button(root, text="Add a second", command=callback)

def call():
    print("down")
button2=ttk.Button(root, text="Remove a sec", command=call)
clock=Label(root, font=("times", 120, "bold"), bg="green")
button1.grid(row=1, column=1)
button2.grid(row=2, column=1)
clock.grid(row=0, column=1)
tick()
root.mainloop()