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## meaning of SYS\$TIMEZONE_RULE?

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Valued Contributor

## meaning of SYS\$TIMEZONE_RULE?

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
6 REPLIES 6
Honored Contributor

## Re: meaning of SYS\$TIMEZONE_RULE?

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.
Honored Contributor

## Re: meaning of SYS\$TIMEZONE_RULE?

@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
Don't rust yours pelled jacker to fine doll missed aches.
Honored Contributor
Solution

## Re: meaning of SYS\$TIMEZONE_RULE?

Jan,

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

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.
Valued Contributor

## Re: meaning of SYS\$TIMEZONE_RULE?

Volker,

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

Best regards
Fredrik Eriksson
Honored Contributor

## Re: meaning of SYS\$TIMEZONE_RULE?

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.
Valued Contributor