Hi Chris,

That makes sense to me.  Still shouldn't myDateAndTime asDate also have no
time-specific information or is there a benefit to it?  The bug persists if
you accidentally create a date from one or the other and compare them.

I'm still struggling to find any reason to have the offset set to a date of
any kind that doesn't have a time attached to it.  It might make sense if
we knew or could sort out dates that didn't belong but with without the
time you don't even know that.  That only reason I can think of would be to
separate dates created in different time zones for reporting but I keep
thinking that even that seems wrong because I wouldn't want to depend on
some obscure feature like that, instead I would make it more explicit and
save the location directly.

I think myDateAndTime asDate should also use the default offset of 0.

All the best,

Ron

On Thu, Sep 5, 2019 at 7:47 PM Chris Muller <asqueaker at gmail.com> wrote:

> I believe Brent developed Chronology from a simple and steadfast
> conceptual model of time:
>
>   - A *point* in time (DateAndTime+TZ)
>   - A *duration* of time (Duration)
>   - A *span* of time beginning from a specific point (Timespan)
>
> Steadfastly to the model, Minute, Hour and Date implementations emerged as
> "spans" of time of those given Durations, and beginning from whatever the
> client-specified point in time was, including TZ.  From there, Chronology
> left it up to clients to do what was necessary to fit their use cases.
>
> The problem is that "Canonical Date" is a use-case is immensely common
> that, yes, it felt like a "longstanding bug" for Chronology not to address
> it.  We finally did in a way that preserves those original tenets of the
> domain.
>
> Best,
>   Chris
>
>
> On Thu, Sep 5, 2019 at 6:08 PM Ron Teitelbaum <ron at usmedrec.com> wrote:
>
>> Hi Chris,
>>
>> Just wondering what the benefit of myDateAndTime asDate holding the
>> timezone information is used for.  Do you report dates based on Timezone
>> from the saved date?  That is the only real benefit I can think of because
>> without the actual time you don't know if the date is wrong for any
>> particular context.  I'm just interested to know how the offset might be
>> used.
>>
>> Thanks!
>>
>> All the best,
>>
>> Ron Teitelbaum
>>
>> On Thu, Sep 5, 2019 at 4:56 PM Chris Muller <asqueaker at gmail.com> wrote:
>>
>>> Hi Sean,
>>>
>>> No.  The recent UTCDateAndTime format change to Squeak made no
>>> difference in this regard.  The example you gave had already been fixed
>>> previously by the introduction of #defaultOffset back in 2012.  Dates
>>> created in non-TZ-specific contexts all get a defaultOffset of 0:00.
>>>
>>> So, in your example, '1/1/1901' asDate has no time-specific information,
>>> so it would inherit the defaultOffset (0:00), which compares favorably to
>>> other Dates with the same offset.  Only Dates which were created via:
>>>
>>>      myDateAndTime asDate
>>>
>>> would inherit the timezone from myDateAndTime, and therefore represent a
>>> different period of time than the ones that began at offset 0:00.
>>>
>>>  - Chris
>>>
>>>
>>>
>>> On Wed, Sep 4, 2019 at 11:52 AM Sean P. DeNigris <sean at clipperadams.com>
>>> wrote:
>>>
>>>> Did the recent changes to Squeak's Date/Time handling (or any 3rd party
>>>> lib)
>>>> ever solve the following longstanding Chronology bug:
>>>>
>>> >Consider this thought experiment:
>>>> > At 11:59pm before DST changes, eval aDate := '1/1/1901' asDate.
>>>> > Now, wait two minutes and at 12:01am eval self assert: '1/1/1901'
>>>> asDate =
>>>> > aDate and… whammo, an exception!
>>>> > The "different" offsets render equal dates unequal depending on when
>>>> the
>>>> > objects were created.
>>>> > The fact that the offset is the one active at object creation is the
>>>> key
>>>> > error, because it should be the offset active when the date occurred.
>>>>
>>>>
>>>>
>>>> -----
>>>> Cheers,
>>>> Sean
>>>> --
>>>> Sent from: http://forum.world.st/Squeak-Dev-f45488.html
>>>>
>>>>
>>>
>>
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