from tkinter import Tk, Label
from datetime import datetime
 
root = Tk()
x, y = root.maxsize()
root.title('Clock')
root.geometry('+{x}+{y}'.format(x=x-200, y=y-150))
root.overrideredirect(False)
 
label = Label(root)
label.pack(expand=True, fill='both')
 
def change_time_date():
    now = datetime.now().strftime('%H:%M:%S')
    today = datetime.today().strftime('%Y.%m.%d')
    time_date = '{}\n\n{}'.format(now, today)
    label.config(text=time_date, bg='#000000', fg='#FFFFFF', font=('Segoi UI', 20, 'bold'))
    label.after(1000, change_time_date)
 
change_time_date()
root.mainloop()

master.attributes("-fullscreen", 1)