Extended Daylight Saving Time


You want the router to automatically adjust to the Extended Daylight Saving Time which takes affect starting in March 2007.


To automatically adjust the router time to account for the new extended Daylight Saving Time, starting in March 2007, use the following commands:

Router2#configure terminal 
Enter configuration commands, one per line. End with CNTL/Z.
Router2(config)#clock timezone EST -5
Router2(config)#clock summer-time EDT recurring 2 Sun Mar 2:00 1 Sun Nov 2:00



The U.S. Energy Policy Act of 2005 includes changes to extend Daylight Saving Time (DST) by one month each to conserve energy. Starting in 2007, DST will begin three weeks earlier, on the first Sunday in November.

In Recipe 14.4, we discussed how to configure the router to adjust the time for DST; however, starting in March 2007, the configuration for most U.S. time zones change, and we need to change the router configuration. Otherwise, the router will continue to abide by outdated and incorrect DST rules.

We can configure the router to follow the new rule using the command shown in the "Solution" section of this recipe:

Router2(config)#clock summer-time EDT recurring 2 Sun Mar 2:00 1 Sun Nov 2:00

This command says that DST begins on the second Sunday in March at 2:00 AM and ends on the first Sunday in November at 2:00 AM (exactly the new rule). Please refer to Recipe 14.14 for more options and information on this command.

Table 14-3 shows the new start and end dates for the extended DST.

Table 14-3. DST dates starting March 2007

Year DST begins 2:00 AM(Second Sunday in March) DST ends 2:00 AM(First Sunday in November)
2007 March 11 November 4
2008 March 9 November 2
2009 March 8 November 1
2010 March 14 November 7
2011 March 13 November 6
2012 March 11 November 4

To view the new the DST information, use the show clock detail command:

Router2#show clock detail
17:07:05.440 EST Sun Jan 28 2007
Time source is NTP
Summer time starts 02:00:00 EST Sun Mar 11 2007
Summer time ends 02:00:00 EDT Sun Nov 4 2007

Notice the configured DST dates now conform to the new extended DST dates.

See Also

Recipe 14.4; Recipe 14.3

Router Configuration and File Management

Router Management

User Access and Privilege Levels


IP Routing





Frame Relay

Handling Queuing and Congestion

Tunnels and VPNs

Dial Backup

NTP and Time


Router Interfaces and Media

Simple Network Management Protocol





First Hop Redundancy Protocols

IP Multicast

IP Mobility




Appendix 1. External Software Packages

Appendix 2. IP Precedence, TOS, and DSCP Classifications


Cisco IOS Cookbook
Cisco IOS Cookbook (Cookbooks (OReilly))
ISBN: 0596527225
EAN: 2147483647
Year: 2004
Pages: 505

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