Jump to content


Photo

NTP daylight saving

Started by Henrik Christensen , 10 March 2017 - 10:06 AM
6 replies to this topic

Henrik Christensen Members

Henrik Christensen
  • 51 posts

Posted 10 March 2017 - 10:06 AM

I need to be sure daylight saving adjustment is NOT happening - how to do that on NetScaler?



Joe Brozzetti Members

Joe Brozzetti
  • 180 posts

Posted 10 March 2017 - 06:19 PM

Netscaler can be configured to use an NTP server.  It gets it time from that so point it to a time server that does not use DST.

 

System > NTP servers

 

You can also use UTC time

 

System > Settings > Change Time Zone

 

https://support.citrix.com/article/CTX120666



Henrik Christensen Members

Henrik Christensen
  • 51 posts

Posted 11 March 2017 - 10:46 AM

Because NTP is based on UTC which does not have a daylight savings time period, the operation systems of servers and clients are solely responsible for switching from/to DST.

 

So back to my initial question: How do I control this on NetScaler besides setting it to UTC (Funny enough in syslog settings, Citrix uses GMT)



Joe Brozzetti Members

Joe Brozzetti
  • 180 posts

Posted 13 March 2017 - 06:51 PM

Sorry If I am not understanding, are you asking how to control Windows Servers/Clients time from Netscaler?  If so, I am not aware of any way to do this with Netscaler.



Paul Blitz Members

Paul Blitz
  • 3,857 posts

Posted 15 March 2017 - 01:22 PM

Many countries don't use daylight saving times, but places like US and UK *do*.

 

Unfortunately, many Americans, including programmers, get UK times confused:

 

UTC : international time, no daylight saving

GMT: within a second of UCT, no daylight savings (not adjusted for summer!!)

BST: = GMT+1 hour: this is the time used in the summer in the UK

"UK Time": reflects GMT in winter, BST in summer.

 

(the confusion is that they use "GMT" to mean "UK Time", so get it wrong for the summer!)

 

I suspect there are similar issues in the US. For example, "Eastern Time" is EITHER "EST" (UTC-5) or "EDT" (UTC-4), depending on time of year.

 

Netscaler lists (mainly) "GMT-4: EDT" (which is technically 100% correct) but also does list some "GMT-5: EST" locations. I'm assuming that, like "GMT" they mis-interpret this to be "EST in winter, EDT in summer", or "Eastern Time, adjusted as needed for Daylight Saving".... and in fact, I thing they mis-interpret GMT in the same way!

 

What is "time"? it's what time my clock shows, here at home.... so daylight savings adjusted. The only guaranteed way to not get Daylight Savings I guess is to use UCT.

 

 

[As I type this, my PC tells me it is 13:20. So that's 13:20 GMT = 13:20 UCT. in 6 months time (after losing an hour's sleep one night) it would be 14:20 BST (= 13:20 GMT = 13:20 UCT).]



Henrik Christensen Members

Henrik Christensen
  • 51 posts

Posted 16 March 2017 - 07:17 AM

Sorry If I am not understanding, are you asking how to control Windows Servers/Clients time from Netscaler?  If so, I am not aware of any way to do this with Netscaler.

No, I just pointed out that a NTP server always give out time without daylight savings, and its the client responsibility to adjust that part. But my conclusion is (also based on Paul's post) that the NetScaler does not have the possibility to enable or disable daylight savings. So I guess my best choice is using UTC for this implementation to be sure.



Rhonda Rowland Members

Rhonda Rowland
  • 111 posts

Posted 16 March 2017 - 05:39 PM

Henrik, if you choose a timezone that doesn't adjust for daylight savings time, then you would also get your result.

For example, Americas/Jamaica (and other equatorial locations, don't use it, usually).

 

The trick is which UTC/GMT offset do you prefer and is there a compatible timezone location without DST adjustments and is it supported on the NetScaler. This may help you find a list of the offsets that may work, and then you can compare if the timezone is on the NetScaler.  (A DST flag might be easier, but since this can be controlled by which timezone you select, it should be equivalent.)

https://greenwichmeantime.com/countries/