DST timezone rules

[martinv]

Hi!

As the DST-to-STD change has just occured in Germany, I have a bugfix request to make. The TZ database for "Europe/Berlin" contains this timezone rule

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CET^1CEST^2,M3.4.0/02,M10.5.0/03

which is WRONG (and has been for as long as I can remember). The correct STD-to-DST rule is "M3.5.0/02" (i.e. not the fourth, but the last Sunday in March).

The reason I bring this up is that for the next STD-to-DST change, the error will strike - the change will not be on 24-Mar-2024, but on 31-Mar-2024.

cu,
Martin

[joukj]

Probably wrong for all CEST zones.... same problem with Europe/Amsterdam

[volkerhalle]

Martin,

DECnet/OSI V6.3 for OpenVMS VAX V6.2 has got it right ;-)

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  "SYS$TIMEZONE_RULE" = "MET-1MET_DST-2,M3.5.0/2,M10.5.0/3"
  
   Version = "DECnet/OSI for OpenVMS Version V6.3-ECO04 27-JUN-1996 23:36:09.95"

The problem may not be to fix this - can you raise a problem report in the VSI Service Platform ? - but to patch all the remaining OpenVMS systems in the field (at least in Europe) before 24-MAR-2024

Volker.

[volkerhalle]

Pointer to an article on 'Troubleshooting OpenVMS Time zone Issues' from the Digital Technical Journal V17, which describes building timezone rule files:

https://www.zx.net.nz/mirror/h71000.www ... oting.html

Hope this helps,

Volker.

[madsweeney]

I am not saying the problem will not exist but the rule you are looking at is the 2023 rule. On January 1, 2024 the rule will be updated to the 2024 rule. Its possible the 2024 rule will correct the problem. I unfortunately do not have a system that can be used to check the rule update that will happen on January 1.

[volkerhalle]

Dave,

I'm deeply impressed:

X86VMS $ sho log *time*zone*rule*

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

X86VMS $ set time=14-jan-2024
X86VMS $ sho time
14-JAN-2024 00:00:02

X86VMS $ sho log *time*zone*rule*

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

They key seems to be the following lines in SYS$COMMON:[SYS$ZONEINFO.SYSTEM.SOURCES]europe.

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Rule    EU      1981    max     -       Mar     lastSun  1:00u  1:00    S
Rule    EU      1996    max     -       Oct     lastSun  1:00u  0       -

Thanks for the clarification.

Volker.

[martinv]

Dave,

I'm baffled - I had no idea that the SET TIME command would update the time logicals. Hopefuly this also happens when the regular rollover to 2024 happens.

(Later) No it doesn't, as the following script shows

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$ type timezone_test.com
$ set time="31-dec-2023 23:59:55"
$ loop:
$   show time
$   show logical sys$timezone_rule
$   wait ::1
$   goto loop
$
$ @timezone_test.com
  31-DEC-2023 23:59:55
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
  31-DEC-2023 23:59:56
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
  31-DEC-2023 23:59:57
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
  31-DEC-2023 23:59:58
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
  31-DEC-2023 23:59:59
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
   1-JAN-2024 00:00:00
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
   1-JAN-2024 00:00:01
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
   1-JAN-2024 00:00:02
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
   1-JAN-2024 00:00:03
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
 *Interrupt*

$

How is the logical adapted to the 2024 value if no SET TIME is issued?

That said, with the new SYS$TIMEZONE_RULE logical the DST-to-STD rule is wrong again (M10.4.0/03 instead of M10.5.0/3), but that's okay as the fourth Sunday in October 2024 will also be the last Sunday.

cu,
Martin

Added in 18 minutes 57 seconds:
Volker,

nitpicking...

They key seems to be the following lines in SYS$COMMON:[SYS$ZONEINFO.SYSTEM.SOURCES]europe.

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Rule    EU      1981    max     -       Mar     lastSun  1:00u  1:00    S
Rule    EU      1996    max     -       Oct     lastSun  1:00u  0       -

But in the same file it is stated that these rules only apply to Western and Eastern Europe, while Central Europe uses the "C-Eur" rules (which state the same rules, only in local time):

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Rule    C-Eur   1981    max     -       Mar     lastSun  2:00s  1:00    S
Rule    C-Eur   1996    max     -       Oct     lastSun  2:00s  0       -

Zone    WET             0:00    EU      WE%sT
Zone    CET             1:00    C-Eur   CE%sT
Zone    MET             1:00    C-Eur   ME%sT
Zone    EET             2:00    EU      EE%sT

<sigh> There's a reason that the VMS FAQ dedicates a whole chapter to Time and Timekeeping....

cu,
Martin

[volkerhalle]

Martin,

could you run your test until 01-JAN-2024 02:05 ?

There is one TQE for JOB_CONTROL at 1-JAN-2024 02:00:49.21 - this may cause the new time zone for 2024 to be set...

$ ANALYZE/SYSTEM
SDA> SET PROC JOB_CONTROL
SDA> SHOW PROCESS/TQE
...
820F4440 00B91FDE.CE1429A0 1-JAN-2024 02:00:49.21 TSA---
SDA> EXIT

Volker.

[martinv]

Volker,

it does make a change:

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   1-JAN-2024 02:00:45
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
   1-JAN-2024 02:00:46
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
   1-JAN-2024 02:00:47
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
   1-JAN-2024 02:00:48
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.4.0/02,M10.5.0/03" (LNM$SYSTEM_TABLE)
   1-JAN-2024 02:00:49
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.5.0/02,M10.4.0/03" (LNM$SYSTEM_TABLE)
   1-JAN-2024 02:00:50
   "SYS$TIMEZONE_RULE" = "CET^1CEST^2,M3.5.0/02,M10.4.0/03" (LNM$SYSTEM_TABLE)

Case closed.

[charles.williams1@covance.com]

If you would like to feel a little more secure that there are actually timer queue entries in place to make the DST changes, this little DCL command procedure will show you. Additionally, it's a nice simple example of using the system analyze utility.