ntp-sync

#!/usr/bin/env python

usage_msg = (
'''Synchronize computer time with a trusted source on the internet
Synopsis:
$ ntp-sync # uses pool.ntp.org
$ ntp-sync CUSTOM-NTP-SERVER
''')

import sys
import subprocess

def print_usage_exit():
    sys.stderr.write(usage_msg)
    sys.exit(2)

args = sys.argv[1:]

if len(args) == 0:
    ntp_server = 'pool.ntp.org'
elif len(args) == 1:
    ntp_server = args[0]
    if ntp_server in set(['-h', '--help']):
        print_usage_exit()
else:
    print_usage_exit()

subprocess.check_call(['sudo', 'ntpdate', '-v', ntp_server])