[Info-vax] Does anyone know if the unsupported TBO (time boost utility that "drifts" time forward or backward by adjusting ticklength) was every ported to the Itanium?

[Stephen Hoffman]

On 2020-10-30 01:27:43 +0000, Chris said:

> How does VMS keep time ?.

OpenVMS and most apps use a quadword value containing centiseconds 
typically configured for localtime, and with few apps having adopted 
the UTC timekeeping that semi-recent OpenVMS versions can also provide.

Here's some general reading on this topic from the old FAQ and from the 
current manuals:
http://www.hoffmanlabs.com/vmsfaq/vmsfaq_004.html#faq_time
https://vmssoftware.com/pdfs/HP_branded_docs_1st_batch/HP_OpenVMS_System_Managers_Manual_Vol1.pdf#page=173 


If after having read through that and should you still have questions, 
stop back and I'll try to either clarify or confuse things more.

C provides the C APIs, as do other languages.

Details here do vary over the versions, with OpenVMS V7.3 and later 
having integrated support for timekeeping and timezones—older releases 
had that data largely in either the IP or DECnet-Plus stack.

V7.3 was when there started to be timezone-related prompts at OpenVMS 
install time, among other updates.

> Does it use ntp, or some system of it's own ?.

OpenVMS uses its own local timebase, unless specifically configured for 
NTP or DECnet-Plus DECdtss.

When OpenVMS and the IP or DECnet-Plus network stack is configured to 
synchronize using NTP or DECdtss, those mechanisms then use system APIs 
to manage and to drift the system time.

NTP presents the system with UTC values, meaning arithmetic to convert 
UTC to localtime.

> Most of the world seems to use UTC +/- offset these days, which seems 
> sensible...

Localtime. And twice a year the localtime value shifts either manually 
or automatically, for those that still "celebrate" DST.

Which is at the core of this thread.

DEC OpenVMS by way of DEC MICA is where Microsoft Windows inherited its 
bad timekeeping ideas from, too.

Put differently, if you could pick a simple and utterly wrong approach 
to timekeeping, that'd be what OpenVMS uses. Heap on ~forty years of 
app upward compatibility, and things get even more muddled.




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