NTP and Daylight Saving Time in North America – Cisco IOS

If you want to set up Central Time (Chicago) on you deice you

ntp server [IP of your NTP 1 server]
ntp server [IP of your NTP 2 server]
clock timezon UTC -6
clock summer-time DST recurring  2  sun march 02:00 first sun nov 02:00

And now we can verify:

#sh clock det
16:17:47.512 DST Thu Apr 25 2013
Time source is NTP
Summer time starts 02:00:00 UTC Sun Mar 10 2013
Summer time ends 02:00:00 DST Sun Nov 3 2013

Look at the US Daylight Saving website to check if you have done it right.