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Understanding DST changes


 This document describe how DST changes and how time changes are implemented in DST.

Daylight Saving Time (DST) is the practice of setting the clocks forward 1 hour from standard time during the summer months, and back again in the fall, in order to make better use of natural daylight.


Time zone information in CUCM is based on the Time Zone Database called the Olson database defined by IANA.  Changes in the Time Zone Database usually happen a couple of times a year, Cisco releases the .cop file for CUCM/Unity/UCCX that includes the changes to the Time Zone Database. Not all of the changes in the Time Zone Database have a respective .cop file for CUCM.


DST changes are performed according to schedule, defined by the time zone data version.


adminprassha: show timezone config

Current time zone: India Standard Time (Asia/Kolkata)

Timezone version: 2015a

In the above example, the installed time zone version is 2015a and the system is set in IST Time zone


I just had India Server installed so added the snippet, but DST is not followed in IST time zone.


If there are DST change schedule for the year can be updated using the COP file released by Cisco every year based on the DST rule. There are many changes in DST across the globe each year, so it is important that you keep the DST schedule updated. DST file is bundle of every time zone information and server time file is changed accordingly after the file updated.


You can run the specific time zone query to verify the time updated:

adminprassha: run sql select * from typetimezone where name ='Asia/Kolkata'

enum name         description                                     moniker               bias stddate             stdbias dstdate             dstbias abbreviation legacyname

==== ============ =============================================== ===================== ==== =================== ======= =================== ======= ============ ===================

37   Asia/Kolkata (GMT+05:30) Mumbai, Kolkata, Chennai, New Delhi TIMEZONE_ASIA_KOLKATA -330 0/0/0/0,00:00:00:00 0       0/0/0/0,00:00:00:00 0       IST          India Standard Time


You can list the available time zone:

adminprassha: show timezone list

  0 - Africa/Abidjan

   1 - Africa/Accra

   2 - Africa/Addis_Ababa

 For changing the time zone you can use the set command:


adminprassha: set timezone 2

 System restart is required when changing the system time zone.


Once the DST file is updated on CCM, Phones will download the updated .tzupdater file from config file and corresponding time will be displayed, this file differs phone models.

You must restart all your phones to take effect after the DST file applied on the CCM TFTP server

Similarly for other Unified servers like UCCX, DST files are applied script/messages are played accordingly

Common Issue after DST implementation reported:

  • Some of the IP phones are displaying the incorrect time : Verify the phone registered with TFTP server has the updated DST file implemented and verify if the phone has downloaded the .tzupdater file if not, perform TFTP service restart and reset the phones.
  • If you have not installed DST file and you have very small setup you can manually change the server time as per local DST time, any way same changes are done by DST files.
  • You might face issue with UCCX script too if you have TOD setup and DST file applied but again your TOD is not taking affect: Verify UCCX server acting locally has DST file applied because in case of TOD UCCX will use the server that is currently acting as a Master, no matter Primary or Secondary it will take the local server time acting as Master, similar steps applied to Unity server as well.
  • Time source can be NTP but the server time <local time> will be as per the DST applied, very important information to keep in mind when troubleshooting on DST issues.


Before restarting the services keep in mind your production impact. 


I hope you will find this document helpful…Happy DST.


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Cisco Employee

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