get the date time from the web site by http head and set it as the system time

set_date_from_http.py

#!/usr/bin/python2

import subprocess
import re
import os
import time

def set_os_date( url ):
        header = subprocess.check_output( ["curl", "--head", url ], shell=False )
        for line in header.split("\n"):
                if re.match(r'^Date:', line ):
                        try:
                                os.system( 'date -R --set="%s"' % line[6:] )
                                return True
                        except:
                                pass
        return False

web_sites = ["http://google.com", "http://baidu.com", "https://github.com"]

while True:
        for url in web_sites:
                if set_os_date(url):
                        break
        time.sleep(10)