US Daylight Rules Changing

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Norton Allen

US Daylight Rules Changing

Post by Norton Allen » Wed Nov 01, 2006 1:45 pm

I have heard that the US is going to have different dates for the daylight
change starting Spring 2007. Is there any documentation for what we'll
need to change to stay current? New TZ definitions?

Eric Johnson

Re: US Daylight Rules Changing

Post by Eric Johnson » Wed Nov 01, 2006 3:03 pm

We have not yet made product changes or developed guidelines relating to
this but are tracking the issue (for Momentics and Neutrino it is Ref#
40378, for QNX 4 is is Ref# 39034 ) for implementation in a future release.

In the meantime, here are some of the thing you might consider:
- for installation of dev seats and x86 runtimes, the default values we use
for DST will be incorrect for the USA locales
(/etc/timezone/uc_tz_t, /etc/TIMEZONE etc.)
- TZ syntax does not include anything that recognizes changes in rules over
time; this means that the TZ setting for systems will need to be changed on
the effective date. The rule cannot be expressed within the TZ variable such
that the changeover happens purely based on the current time.
- any applications that convert UTC times to localtime may need to be aware
that their local time conversions of old dates will be incorrect for
dates/times in the affected intervals
- the default 'shorthand' rules built into TZ interpretation will now be
wrong
for affected areas (e.g. EST5EDT will now produce incorrect results for such
an
area)

Hope that helps.

- Eric

"Norton Allen" <allen@huarp.harvard.edu> wrote in message
news:eia8ec$q2k$1@inn.qnx.com...
I have heard that the US is going to have different dates for the daylight
change starting Spring 2007. Is there any documentation for what we'll
need to change to stay current? New TZ definitions?

Carlos Clarke

Re: US Daylight Rules Changing

Post by Carlos Clarke » Fri Jan 12, 2007 8:11 pm

Any update on this?
Isn't the change supposed to happen in mid-March?
Doesn't give us much time to make updates.

Carlos

On Wed, 1 Nov 2006 10:03:03 -0500, "Eric Johnson" <eric@qnx.com>
wrote:
We have not yet made product changes or developed guidelines relating to
this but are tracking the issue (for Momentics and Neutrino it is Ref#
40378, for QNX 4 is is Ref# 39034 ) for implementation in a future release.

In the meantime, here are some of the thing you might consider:
- for installation of dev seats and x86 runtimes, the default values we use
for DST will be incorrect for the USA locales
(/etc/timezone/uc_tz_t, /etc/TIMEZONE etc.)
- TZ syntax does not include anything that recognizes changes in rules over
time; this means that the TZ setting for systems will need to be changed on
the effective date. The rule cannot be expressed within the TZ variable such
that the changeover happens purely based on the current time.
- any applications that convert UTC times to localtime may need to be aware
that their local time conversions of old dates will be incorrect for
dates/times in the affected intervals
- the default 'shorthand' rules built into TZ interpretation will now be
wrong
for affected areas (e.g. EST5EDT will now produce incorrect results for such
an
area)

Hope that helps.

- Eric

"Norton Allen" <allen@huarp.harvard.edu> wrote in message
news:eia8ec$q2k$1@inn.qnx.com...

I have heard that the US is going to have different dates for the daylight
change starting Spring 2007. Is there any documentation for what we'll
need to change to stay current? New TZ definitions?


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