[squeak-dev] About the new Date

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Fri Feb 10 21:52:26 UTC 2012

2012/2/10 Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>:
> 2012/2/10 David T. Lewis <lewis at mail.msen.com>:
>> On Fri, Feb 10, 2012 at 08:22:34AM +0200, Brent Pinkney wrote:
>>> Hi,
>>> One thing we can consider is a DynamicBinding that specifies the offset. If no binding, then use the global default.
>>> This is how lisp/scheme would solve it.
>> Hi Brent,
>> That might be a good approach. I did something like that with the
>> TimeZoneDatabase tables, such that the current time zone is a proxy
>> that points to the Olsen time zone tables, and "DateAndTime
>> localTimeZone offset" finds the proper offset in the tables. This
>> works well.
>> Having said that, I think that Chris' original idea was to use only
>> the UTC-based (#globalize) style, and to rely on idioms like
>> "DateAndTime now asDate" to create an instance of Date with an
>> offset for local time zone. Having played around with the inbox changes
>> a bit now, I have to say that I think Chris was right, it's is probably
>> better to keep things simple and consistent, and not try to have a
>> #localize variant.
>> Do you (Brent) have a preference on this? For myself, I'm happy
>> with Chris' proposal (minus the #localize feature, which I suspect
>> that Chris will be more than happy to remove ;)
> +1 again, I like DateAndTime>>midnight to use receiver offset, and
> consequently asDate too, it's the least surprising...
> Well, it won't perfectly handle those legal days when DST change and
> which are not 24h long, but it's already better than what we have.
> Now, if you don't have a local zero offset, you'll get
> (Date newDay: 10 month: 2 year: 2012) = Date today = false
> So maybe we need to have this kind of method on instance side:
> Date>>withoutOffset "Note: it's makeUTC without statefull side effects"
>    "Answer the same day without any time zone offset."
>    ^self withOffset: 0 hours
> Date>>localize "or local or localTime or ?"
>    "Answer the same day starting at midnight local time"
>    ^self withOffset: DateAndTime localOffset
> Date>>withOffset: aDuration
>    "Answer the same day in a different time zone"
>    ^self starting: (start copy primOffset: aDuration asDuration)

^self class of course, hey, I shouldn't write code in mail

> Nicolas
>> Dave

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