tag:blogger.com,1999:blog-1823047306722101134.post3761249304998562619..comments2022-04-28T15:00:09.362-05:00Comments on Spyglass' Ramblings: How Microsoft Botched DST 2007Glen Mark Martinhttp://www.blogger.com/profile/06592122769805439088noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-1823047306722101134.post-75482098784401772592007-03-14T09:57:00.000-05:002007-03-14T09:57:00.000-05:00Yes and no. We're both a little wrong on this. I g...Yes and no. We're both a little wrong on this. I grossly overgeneralized the problem for OpenVMS. (Hoff would be so ashamed of me...) From <A HREF="http://h71000.www7.hp.com/faq/vmsfaq_005.html" REL="nofollow">http://h71000.www7.hp.com/faq/vmsfaq_005.html </A>: <BR/><BR/><B>"4.1.1.2.2 EXE$GQ_SYSTIME This is the OpenVMS Alpha system time cell. This cell contains the number of 100ns intervals since November 17, 1858 00:00:00.00. This cell is incremented by 100000 every 10ms by an hardware interval timer."</B> <BR/><BR/>What the FAQ doesn't mention is that the value returned by EXE$GQ_SYSTIME is set relative to local time. Two systems in adjacent time zones will have their system time cells differing by about an hour. (If I am in error about this, please feel free to correct me.) <BR/><BR/>UTC is calculated from this using the TDF. <BR/><BR/>Of course, VAX used the TOY (Time of Year) clock, which was pretty limited. I haven't seen any info on how Itanium OpenVMS systems track time. <BR/><BR/>The only OpenVMS system I still maintain is still running v7.2-1, from a period when OpenVMS was still pretty clueless about DST and has to be manually adjusted twice a year. The way this version handles conversions from EXE$GQ_SYSTIME, the clock might as well be ticking local, although my reading indicates that more recent versions handle timezones and DST much better. (I really should download a copy of <A HREF="http://www.personalalpha.com" REL="nofollow">PersonalAlpha</A> and a <A HREF="http://www.openvmshobbyist.org/" REL="nofollow">Hobbyist license</A> to take a more up-to-date version for a spin and keep my feet wet. Sadly, the VMS box I manage for work will be retired by the end of the year.) On top of this, prior to OpenVMS v6.0, the system had no concept of UTC or TDF (although the UCX TCP/IP stack did). <BR/><BR/>There is a great discussion of OpenVMS and timezones at <A HREF="http://h71000.www7.hp.com/faq/vmsfaq_006.html" REL="nofollow">http://h71000.www7.hp.com/faq/vmsfaq_006.html </A>.Glen Mark Martinhttps://www.blogger.com/profile/06592122769805439088noreply@blogger.comtag:blogger.com,1999:blog-1823047306722101134.post-36729978975691887232007-03-13T11:27:00.000-05:002007-03-13T11:27:00.000-05:00> a design flaw shared by OpenVMSAnd fixed 10+ yea...> a design flaw shared by OpenVMS<BR/><BR/>And fixed 10+ years ago. The system clock is now in UTC, and a "Time Differential Factor" (TDF) is applied to get local time.Stanley F. Quaylehttps://www.blogger.com/profile/00158322131691948596noreply@blogger.comtag:blogger.com,1999:blog-1823047306722101134.post-72104251969064243072007-03-13T11:26:00.000-05:002007-03-13T11:26:00.000-05:00> a design flaw shared by OpenVMSAnd fixed 10+ yea...> a design flaw shared by OpenVMS<BR/><BR/>And fixed 10+ years ago. The system clock is in UTC, and there's a "Time Differential Factor" (TDF) to get local time.Stanley F. Quaylehttps://www.blogger.com/profile/00158322131691948596noreply@blogger.com