This a recurring topic in the mailing list. See: http://forum.world.st/Interesting-Date-Time-Thread-on-Squeak-Dev-td4778652.html#a4778970
Or directly go to this https://www.w3.org/TR/timezone/ Pharo's Date and Time classes are incremental/offset based, whereas a field based Date behaves more as "expected" in terms of adding days/months/days/hours/etc. The internal implementation might vary and there are going to be tradeoffs, but IMO for scheduling solutions calendar based are better suited. Regards! On 10/04/2018 11:13, Stephane Ducasse wrote: > What is a field based date and time? > > On Tue, Apr 10, 2018 at 1:32 PM, Esteban A. Maringolo > <emaring...@gmail.com> wrote: >> What is missing in the current Pharo image is a field based >> Date/DateTime instead of an offset+duration one as it currently is. >> >> Why not use Chronos instead? AFAIR Chronos provides that. >> >> An alternative would be to implement a "Calendar" (as in >> Java.util.Calendar [1]), that can exist in parallel with the existing >> Date class. >> >> Regards, >> >> [1] https://developer.android.com/reference/java/util/Calendar.html >> >> On 10/04/2018 03:30, Stephane Ducasse wrote: >>> Hi Paul >>> >>> I agree and instead of patching the current system I would start using >>> TDD to design >>> a new Date package. >>> >>> stef >>> >>> On Mon, Apr 9, 2018 at 8:42 PM, Paul DeBruicker <pdebr...@gmail.com> wrote: >>>> I think #= is a bad selector for Date and should be avoided when >>>> determining >>>> whether something happens on a date, or whether two dates are the same. >>>> We >>>> all know March 24th in London covers a different 24 hours than March 24th >>>> in >>>> Hawaii but Date>>#= does not. >>>> >>>> >>>> >>>> I think whats needed are more descriptive selectors like >>>> >>>> >>>> Date>>#isSameOnDateAs: aDateOrDateAndTime >>>> Date>>#overlapsWithDate: aDate >>>> DateAndTime>>#occursOnDate: aDate >>>> DateAndTime>>#sameHMSButDifferentUTCIn: aTimeZoneKey >>>> DateAndTime>>#sameUTCButDifferentHMSIn: aTimeZoneKey >>>> >>>> and change Date>>#= to #shouldNotImplement. >>>> >>>> >>>> FWIW I also don't like #offset: as before you send it you know the timezone >>>> and after you may let that knowledge be forgotten. Real offsets can change >>>> as laws change. >>>> >>>> >>>> >>>> I think people are aware of this but if you have need for comparing dates & >>>> times then you must use a library that accesses the regularly updated Olson >>>> timezone database on your system and classes that respect time zones. Time >>>> zones are political, and legal definitions of offsets can change hours >>>> before the DST transition dates & times. >>>> >>>> >>>> I don't think it matters which default timezone you pick for the image if >>>> you're not going to take them into account when doing comparisons. >>>> >>>> >>>> Unfortunately there isn't a way to avoid this complexity until DST goes >>>> away. >>>> >>>> >>>> There's certainly flaws to how we currently do it and I think >>>> TimeZoneDatabase and Chronos make good attempts to fix it. I haven't >>>> looked >>>> at Chalten but would guess its good too. >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> Sean P. DeNigris wrote >>>>> I was bitten by this very annoying bug again. As most of us probably know >>>>> due >>>>> to the steady stream of confused ML posts in the past, the bug in summary >>>>> is >>>>> that we have an incomplete timezone implementation that doesn't properly >>>>> take into account historical DST changes. This flares up without warning >>>>> especially when DST toggles. I created a wiki page to document the >>>>> situation: https://github.com/seandenigris/pharo/wiki/Time-Zone-Fiasco >>>>> >>>>> Here's an example blowup: 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 more I think about it, the more I think that we should just assume UTC >>>>> for all Date[AndTime]s that don't explicitly specify an offset, rather >>>>> than >>>>> pretend to set an offset which is only sometimes correct. More advanced >>>>> users can use one of the available libraries to get full timezone support. >>>>> What do you think? >>>>> >>>>> >>>>> >>>>> ----- >>>>> Cheers, >>>>> Sean >>>>> -- >>>>> Sent from: http://forum.world.st/Pharo-Smalltalk-Developers-f1294837.html >>>> >>>> >>>> >>>> >>>> -- >>>> Sent from: http://forum.world.st/Pharo-Smalltalk-Developers-f1294837.html >>>> >> -- >> Esteban A. Maringolo >> -- Esteban A. Maringolo
