Enter in config mode:
router#configure t
First configure a DNS server to resolve ntp servers name:
router(config)#ip name-server 8.8.8.8
Now set a primary ntp server:
router(config)#ntp server 0.europe.pool.ntp.org
And also a secondary:
router(config)#ntp server 1.europe.pool.ntp.org
Finally configure the time zone, here CET + 1:
router(config)#clock timezone CET 1
Exit from configuration mode and test the status, usually is necessary to wait for a few minutes to get a successful synchronization. Output can be similar to this:
router# show ntp status Clock is synchronized, stratum 3, reference is 178.16.23.50 nominal freq is 249.9684 Hz, actual freq is 249.9665 Hz, precision is 2**16 reference time is DA07DA35.B8AE53C5 (15:40:20.721 CET Tue Ago 4 2015) clock offset is -0.0009 msec, root delay is 0.11 msec root dispersion is 0.08 msec, peer dispersion is 0.01 msec loopfilter state is 'CTRL' (Normal Controlled Loop), drift is 0.000007607 s/s system poll interval is 1024, last update was 567 sec ago.
And test the association server status too:
router# show ntp associations address ref clock st when poll reach delay offset disp *~178.16.23.50 75.12.230.181 2 907 1024 377 86.323 -0.927 13.845 ~37.247.53.178 129.242.4.241 2 904 1024 377 86.323 -0.927 14.845 * sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured