Cisco Correct Time

Short post before I forget -- don't know the extent of its uses beyond log / debug messages, but I would really like my router to know what time of the day it is... and properly update / compensate for summer time.

Before I go any further, you need to know that in Athens ( Greece ), timezone is EET ( Eastern European Time or UTC+2), though it's quite simple to adjust for any other. Summer time ( or daylight saving time) applies from the last Sunday in March to the last Sunday in October (WikiPedia), and changes time to EEST (Easter European Summer Time, or UTC+3). Fortunately IOS knows about this behavior, and allows its programming:

Router(config)# clock timezone EET 2

Router(config)# clock summer-time EET recurring last Sun Mar 3:00 last Sun Oct 3:00
This snippet defines a new timezone called EET that is 2 hours ahead of UTC ( UTC+2 ). It then defines a recurring change of time from last Sunday in March at 3:00am until the last Sunday in October, 3:00am

Of course, just to be safe, after you save this in your configuration you should set the time again, since it will automatically be set two hours ahead ( Cisco only hold UTC time, and adjusts accordingly) by :
Router# clock set 00:00:00 01 Jan 2000
Note that you don't have to specify UTC time, your router assumes you're setting your local time, and will deduct the timezone difference automatically.

Enjoy :P