[squeak-dev] DateAndTime - offset just bit me

Chris Cunningham cunningham.cb at gmail.com
Tue Mar 14 15:26:13 UTC 2017


HI.

On Tue, Mar 14, 2017 at 8:13 AM, Eliot Miranda <eliot.miranda at gmail.com>
wrote:

> Hi Levente,
>
> On Tue, Mar 14, 2017 at 2:41 AM, Levente Uzonyi <leves at caesar.elte.hu>
> wrote:
>
>> Hi Eliot,
>>
>> I pointed out earlier that the time zone doesn't update in primitive 241
>> or primitiveUtcWithOffset when DST changes happen.
>> However, it does change in LocalePlugin's primitiveTimezoneOffset, which
>> is what we use as a workaround to create correct DateAndTime instances in
>> one of our projects.
>> It would be nice if the other two primitives worked correctly.
>
>
> Sure, but the point is that we don't want the normal time access primitive
> to update the timezone in 241 because that adds overhead to every
> invocation that pays off only twice a year.  As David points out
> primitiveUtcWithOffset /does/ update the timezone.  So what's needed is a
> way to arrange that primitiveUtcWithOffset is invoked often enough to
> update the timezone, but infrequently enough not to cost a lot.
>

To be precise, some places change 4 times a year (double daylight savings);
some never change.
If there was a way to know what the local rules were at image startup, it
could schedule a process to kick off around the right time to check for
changes - or it could completely disable that checking.  Most of the year
checking for changes is always no needed (unless the image starts up in a
different zone, at which time it should immediately get the right offset).
I don't have an actual suggestion (yet) on how to know when to start
scanning for changes more regularly.  Maybe it could scan in the high
priority background every 10 minutes for an offset change?

-cbc
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