[time-nuts] Accurate timestamping on computers (previously: For mywhole life timezones have been weird)

[Sarah White]

On 11/3/2012 3:12 PM, David J Taylor wrote:
> -----Original Message----- From: Sarah White
> 
> Great, thanks for the loopstats.
> 
> For the included loopstats, I believe "Alta" was among the ones on which
> you were running windows 7 + NTP... Would you mind confirming which
> setting you have for your timezone? (since I'm reasonably certain I know
> what the timezone menus would look like)
> 
> http://inkushi.freeshell.org/bst.png
> http://inkushi.freeshell.org/utc.png
> 
> Windows has more than one entry for most UTC offsets (DST schedule
> varies by hemisphere, country, some don't have summer time at all, etc.)
> ... so the timezone I personally have selected is the UTC option without
> a summer time adjustment (never set to UTC+01 / BST)
> 
> ... Also, curious what you mean when you say you have "wall clock" time
> displayed (UTC internally) ... ?
> 
> --Sarah
> =================================================
> 
> Sarah,
> 
> PC Alta is Win-7/64, with a GPS/PPS ref-clock using Dave Hart's
> serialPPS.sys device driver.  The time-zone on all my PCs is "London,
> Edinburgh, Dublin", which implies GMT (i.e. UTC) in the Winter and BST -
> British Summer Time  - (UTC+1) in the Summer.  I.e.
> 
>  http://inkushi.freeshell.org/bst.png
> 
> What I mean by wall-clock time is that I have the "standard" settings in
> the control panel, i.e. telling Windows that I am located in Edinburgh
> so that the time displayed by normal applications alters with the
> season, and that the time agrees with normal wall-clock time.  This is
> nothing special, and how almost all PCs in the UK would be set.  I mean
> that I have /not/ set "Casablanca" where there both Summer and Winter
> are UTC.
> 
> I did have one PC set to "UTC only" and NTP ran equally well on it.  As
> I mentioned, internally Windows runs on UTC, and a program can
> interrogate that time.  Windows also provides offsets so that UTC can be
> converted to local (wall-clock) time for display within applications. 
> NTP uses the internal UTC time and is unaffected by time-zone or
> seasonal changes.
> 
> Cheers,
> David

Ah. Ok, cool. I guess the "synthetic timebase" used by NTP is probably
doing what it was meant to do (ignore inconsistency in the RTC under
various circumstances)

By the way, I suspect that you didn't know that morocco (casablanca) has
observed a "summer time" adjustment since the year 2008. I sure didn't.

http://www.timeanddate.com/news/time/morocco-dst-2012.html

Apparently there is now even a "special case" during the muslim month of
ramadan:

-(quote: timeanddate.com)-
According to the new law, the DST period will be interrupted during the
Muslim month of Ramadan (July 20 – August 20, 2012 in the Gregorian
calendar)
-(end quote)-

Earlier I was looking for a UTC timezone to use on my android phone, and
nearly set it to casablaca without fact-checking first... Oops!

For now I suppose that can be one of my clocks set to local time (NY)
since it's a well-known timezone I shouldn't have to worry about too much.

--Sarah

P.S. Seems strange that the only two options for a UTC+0 timezone are
"London, Dublin" or "Casablanca" (neither of which are year-round UTC)
... I'll try to remember to point this out to the cyanogenmod team
(running an aftermarket version of android, cyanogenmod on my phone) so
it can be fixed in the next release.