python klok en elke 5 minuten een update?

import pygame, time
from datetime import datetime
global starttime, endtime

starttime = time.time()
endtime = starttime +300

BLUE = (0, 0, 255)


def klok_datum():
    global klok
    now = datetime.now()
    starttime = time.time()
    klok = now.strftime("%H:%M:%S")

    if endtime < starttime:
        update_nieuws()



def update_nieuws():
    endtime+=10
    print("nieuwe nieuwsitems ophalen")
    #quit()


def kader():
    font = pygame.font.SysFont("comicsansms", 50)
    screen = pygame.display.set_mode((480,320))
    screen.fill((255, 255, 255))

    #show time in kader
    pygame.draw.rect(screen, BLUE, (120, 115, 225, 50))

    klok_datum()
    textklok = font.render(klok, True, (255, 0, 0))
    screen.blit(textklok, (340 - textklok.get_width(), 175 - textklok.get_height()))
    pygame.display.flip()
    clock = pygame.time.Clock()

pygame.init()

done = False
while not done:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True
    kader()

starttime = time.time()
endtime = starttime +300

import time
from datetime import datetime
t=time.time()

def klok_datum():
    now = datetime.now()
    klok = now.strftime("%H:%M:%S")
    print (klok)

def update_nieuws():
    print ("Nieuwsitems ophalen")


while True:
    if time.time()-t>5:
        update_nieuws()
        t=time.time()
    klok_datum()