Daylight saving come up soon

[Andreas Leitgeb]

What sparked this was a report about timestamps changing on XP I
received in an email:

"When the time switches due to DST, the timestamps of all the files on
my PC change by one hour. ..."
I also noticed on my own machine that Winzip seemed to think many
files that have not changed had changed, just after the DST flip on
Vista. ...

On what OSes is this cleverer file classifying behaviouryou described
exhibited?

I see it on linux (through the "date"-utility) and assume it's also
that way on all unices.

The very idea of DST has always offended me, and horrified me once I
realised all the protential for disaster and error it creates. The way
we measure time should not be fiddled with.

Time is a beast
It starts that going round the sun takes a bizarre factor of 365.24...
times longer than the rotation round earths own axis, and with that
axis being not perpendicular to the trip around the sun...

The farther away from equator one is, the more varies the length of day
throughout the year. DST is (imho) an appropriate means to account for
that. If it weren't for all those lots of clocks/watches/... that still
need to be adjusted manually, I'd even prefer a smooth switch, say five
minutes every couple of days. It's like in the former days, when
"morning" was declared by a **** who cried when the sun was coming up.
It surely didn't cry at the same time every day

Given the global village we now like in, I think we should start
thinking about using UTC for any communication that could conceivably
span time zones.

We must accept, that in this global village there is no time where all
are awake at once. And since we already have timezones, we can just
as well also have DST - at least in those parts of the world where
length of daylight time varies enough that it matters.

Just recently they published a study, that DST costs a lot of energy,
but I never trust any such studies except those I faked myself

 

[Martin Gregorie]

java.lang.System.currentTimeMillis nominal resolution is measured in
ms. It seems to me I have seen resolution higher than 18 ticks a
second, so at least that must to looking at a higher resolution timer.

It seems to me I noticed something around the time of NT that lead me
to believe system time was being handled more accurately, but that was
a long time ago and I can't recall details.

I recall though dealing with ticks and lost ticks in DOS.

AFAIK that method persisted as long as Windows was a graphical shell for
DOS, i.e. up to the demise of ME. I would hope that NT and its
successors used a better method, but you never know with Redmond -
there's far too much NIH syndrome in that organization for my taste.

 

[Martin Gregorie]

Even with a GPS there are factors to consider:

- At the NMEA standard bitrate of 4800 bps, it takes nearly 100ms just
to send a short sentence like ZDA (date and time).

- Some GPS units only send data at specific intervals, not necessarily
at the exact time the data was ready, and it gets worse if the unit
has a lot of data to send at a particular moment.

So when was that timestamp you just read from the device actually
taken?

Fair points. MSF with a home-built 30 quid receiver takes a lot of
beating. However, if you're outside the broadcast service areas I reckon
a consumer GPS receiver running off a wall-rat PSU has a pretty good
cost/performance ratio. Its main drawback is that you can only get UTC
from it, so you'd better not be using a system that sets its HW clock to
locale time.

Lets face it - if you're really bothered about time you'll have an
on-site atomic clock and many $$$$ worth of synchronization kit to go
with it.

 

[Arne Vajhøj]

In comp.lang.java.programmer message <[email protected]


(a) I go by what he wrote, not what he might have meant.
(b) Newfoundland is a part of Canada.

Yes - but what he wrote is true for Newfoundland, so that is
not so relevant.

Arne

 

[Roedy Green]

Last I heard all versions of Windows still set the BIOS clock to wallclock time
not UTC, and messed with the BIOS clock for DST. This is hackery to me. Is that
not still the case?

In Vista you change the timezone, the system time automatically
changes so that the system time in UTC is preserved.

Also the file dates all change to the local timezone.

This implies the dates are stored in UTC.

In DOS they were just wall clock time.

In early Windows I think they were wall clock time in standard time,
possibly wall clock time.

I just an email from the Winzip people saying they just use raw
display dates and will stay that way since so few people have
complained.

 

[Dr J R Stockton]

In comp.lang.java.programmer message <[email protected]

Yes - but what he wrote is true for Newfoundland, so that is
not so relevant.

What he originally wrote is not true for Newfoundland. You should have
read back further to avoid the risk of making a foolish response.

 

[Dr J R Stockton]

In comp.lang.java.programmer message <57sbt31c59nvtgdd7bam9j5obpooejlt74
@4ax.com>, Tue, 11 Mar 2008 02:44:50, Roedy Green <see_website@mindprod.
com.invalid> posted:

In Vista you change the timezone, the system time automatically
changes so that the system time in UTC is preserved.

One does not select the time zone directly; one selects the Time Rules,
by choosing a set of locations. Iceland, the British Isles, and Senegal
are all in the same Time Zone, but the BI Rules differ from the others.
Ottawa and Lima are in the same zone, but have different Rules.

 

[Arne Vajhøj]

In comp.lang.java.programmer message <[email protected]


What he originally wrote is not true for Newfoundland. You should have
read back further to avoid the risk of making a foolish response.

Let me get this correct:
- you want to criticize Roedy considering only what was quoted
- you feel exempted from criticism because of something not quoted
?

Hmmmm.

It does not seem to be fairnes or intelligence that fill your life.

Arne




Arne

 

[Roedy Green]

What he originally wrote is not true for Newfoundland. You should have
read back further to avoid the risk of making a foolish response.

The only thing different about Newfoundland's DST is they flip at
12:01 AM rather than 2:00 AM. So I would hardly call his response
"foolish".

There is also a series of running jokes about Newfoundland Standard
time being UTC-3.5, but that is independent of DST.

It makes no practical difference for most people since the change the
clocks before they go to bed, or it happens automatically while they
sleep.

 

[Dr J R Stockton]

In comp.lang.java.programmer message <vhcht3dscr927vupnpvervk6cmmn6j2ci3
@4ax.com>, Thu, 13 Mar 2008 04:56:57, Roedy Green <see_website@mindprod.
com.invalid> posted:

The only thing different about Newfoundland's DST is they flip at
12:01 AM rather than 2:00 AM. So I would hardly call his response
"foolish".

But you referred to North America changing at 02:00. He has shown no
sign of understanding the difference between 00:01 and 02:00. It may
not affect many people, but it does exist.