meaning of SYS$TIMEZONE_RULE?

[Fredrik.eriksson]

Hi all,

Just a quickie check, what does the numbers stand for in the SYS$TIMEZONE_RULE logical?

"SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.5.0/02,M10.4.0/03"

I know that CET^1 CEST^2 tells OpenVMS that after the first comma is the setting for going to summertime (M3 says month 3 (mars), 5 says 5th sunday in the month and /02 says at 02.00) and that the second is for going to CEST.

But what does it mean when it says 5th sunday. There will only be 4 sundays in the month March 2010, is the 5 an automatic function to tell it to change on the last sunday of the month?

And what does that 0 stand for im M3.5.0/02?

Best regards
Fredrik Eriksson

[Volker Halle]

Fredrik,

the 5th sunday is supposed to mean the LAST sunday in the month. There could be months with 5 sundays, so '4' would be wrong. You still see a Mx.4.0/xx in some older versions of OpenVMS, but that's wrong !

0 is for the weekday, i.e. sunday.

Hoff has a good description on his website:

http://labs.hoffmanlabs.com/node/560

Volker.

[Jan van den Ende]

@Volker:

So, if I read you correct

>>>
There could be months with 5 sundays, so '4' would be wrong. You still see a Mx.4.0/xx in some older versions of OpenVMS, but that's wrong !
<<<

then
>>>
"CET^1CEST^2,M3.5.0/02,M10.4.0/03"
<<<

is to mean going back is the 4TH, and NOT the LAST sunday of month 10 (october)?

Or does that need to be corrected before octber will have 5 sundays (which happens to be 2010!!).

It looks we will need patches FOR ALL active versions SOON!!!

Proost.

Have one on me.

jpe

[Volker Halle · Accepted solution]

Jan,

for an explanation, see the entry from Hans Bachner dated 28-MAR-2008 in the following thread:

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1112496


When SYS$TIMEZONE_RULE is set, the calculation always reflects the situation in the year in question. As the last Sunday in October 2007 is the fourth Sunday, you see "M10.4.0/03" in the rule logical. In a year with five Sundays in October, the logical name will show "M10.5.0/03".


So M10.4.0/03 is correct in 2009, but should automatically change to M10.5.0/03 in 2010. Let's see...

Volker.

Volker.

[Fredrik.eriksson]

Volker,

If I understand that correctly then 2010-03-28 this issue will correct itself?

Best regards
Fredrik Eriksson

[Volker Halle]

Fredrik,

last time I checked, the display of the rule was correct on 1-JAN of the new year.

If you're using AUTO_DLIGHT_SAV=1, you'll see that JOB_CONTROL will have a TQE set for the next DST switch or 1-JAN next year. At that time, it will re-calculate the timezone rule.

Volker.

[Fredrik.eriksson]

Got the answer,

Basically M3 says month 3, 5 last day in the month based on 0-7 weekdays where 0 is sunday and /02 is the hour where it changes.

Even thou it says wrong date for october next year it _probably_ will fix itself 1-JAN-2010 since I'm using AUTO_DLIGHT_SAV=1.

Thanks for the help :)

Best regards
Fredrik Eriksson