NX-OS - clock summer-time - Last sunday for BST?

[robdowson]

Hiya,

This may be a dumb question - I may just be missing something obvious - but I'm trying to setup some NX-OS based devices (5548Ps/5020s/1000Vs) with the correct daylight savings setting for the UK - ie. british summer time.

The definition of BST is:

"British Summer Time (BST) starts on the last Sunday in March and ends on the last Sunday in October, at 1.00 am Greenwich Mean Time (GMT)"

ie. it's always the 'last' sunday'. On our IOS devices we do this:

     clock timezone GMT 0
     clock summer-time BST recurring last Sun Mar 1:00 last Sun Oct 1:00

....but there's no equivalent 'last' keyword on NX-OS:

clock summer-time zone-name start-week start-day start-month start-time end-week end-day end-month end-time offset-minutes

Sometimes the 'last' sunday is the 4th, and sometimes it's the 5th...?

Anyone know how to set it to the last sunday? Or do I just have to accept it's sometimes going to be a week out?

Thanks,

Rob...

[Jerry Ye · Accepted solution]

I think you need to use 5

N7K-1(config)# clock summer-time BST ?

  <1-5>  Week number to start (first week=1, last week=5)

Regards,

jerry

[robdowson]

Thanks Jerry,

I'd just spotted that myself aswell - but wasn't sure whether to take that at face value or whether it's just the wording in the help text?

Have you - or has anyone - confirmed this actually works as we expect it to? I don't have a spare nexus switch lying around doing nothing that I can mess about with the clock on to test! I guess we'll find out in a few month's time!

Thanks,

Rob...

[robdowson]

Looks like you're right Jerry! Thanks!

Just managed to find a switch to test it on - and it works as expected:

switch-n5k(config)# sh run | inc clock
clock timezone GMT 0 0
clock summer-time BST 5 Sunday March 01:00 5 Sun Oct 01:00 60
switch-n5k(config)# sh clock
00:56:38.908 GMT Sun Mar 27 2011
switch-n5k(config)# sh clock
02:02:59.779 BST Sun Mar 27 2011
switch-5k(config)#

Thanks,

Rob...

[BTSC BTSC]

The problem is that there isn't always five Sundays in March.

For example, 2016 only has four, as does 2017 and 2018. Then 2019 and 2020 have five, and then back to four for 2021, 2022, 2023.

I obviously don't expect to have the platform in the network that long, but to have to keep changing this in NX-OS is crazy.

Seems like NX-OS has taken a step back in time!!! 

[andy.stallwood · Accepted solution]

Apologies for the necro bump. For anyone else that has come across this years later (like me), it doesn't matter if there are 4 or 5 Sundays in the month. If you put 5, then NX-OS knows you mean the last one (as per the help text).

PS Also, clock change happens at 02:00 in Oct, not 01:00 (https://www.gov.uk/when-do-the-clocks-change) so the correct command is :-

"clock summer-time BST 5 Sunday March 01:00 5 Sun Oct 02:00 60"