Cisco IOS Cookbook, 2nd Edition

Setting the Time Zone

Problem

You want to change the time zone on the router.

Solution

To configure the router’s local time zone, use the following configuration command:

Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#clock timezone EST –5
Router(config)#end
Router#

The clock timezone configuration command accepts any freeform zone name (EST, PST, Eastern, etc.), followed by an offset from the UTC (–24 to 24 hours) and an optional offset from UTC in minutes for areas that require it.

Discussion

By default, the router uses UTC, also called Coordinated Universal Time. UTC, formerly known as Greenwich Mean Time (GMT), has become the worldwide standard for time and date. The principles for calculating local time zones from UTC are the same as for GMT. The only difference is that UTC is based on precise atomic clocks, shortwave radio signals, and satellites to ensure accuracy, which need not actually be located in Greenwich, England.

It is useful to set the router’s internal system clock to display the time in the local time zone. North American clocks set to UTC, for example, display the time between five and eight hours ahead of the local time. This means that somebody reading the clock has to do some mental arithmetic to translate to local time, which is sometimes awkward and makes correlating the times of network problems more difficult than it needs to be.

You can view the current time zone information with the show clock detail command: ...