Cisco IOS Cookbook, 2nd Edition

Extended Daylight Saving Time

Problem

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

Solution

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
Router2(config)#end
Router2#

Discussion

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 Otherwise, the router will continue to abide by outdated and incorrect DST rules.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 EDTrecurring 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.

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