> On 13 Nov 2014, at 15:23, John Joyce <[email protected]> wrote:
>
>
>> On Nov 13, 2014, at 9:54 PM, Jonathan Mitchell <[email protected]>
>> wrote:
>>
>> I have an app that must process sqlite hosted data that contains Gregorian
>> UTC dates.
>> I want to ignore the local locale entirely and use Gregorian UTC through out.
>>
>> At present I am carefully configuring all my NSDatePickers controls and all
>> NSDateComponents calculations to use a specified Gregorian UTC timezoned
>> calendar.
>>
>> Is this the best I can do, or am I missing a trick somewhere?
>>
>> .NET has the concept of a thread culture that defines this sort of thing for
>> a given thread..
>>
>> Thanks
>>
>> Jonathan
>>
> If you want to present things to users well, it is generally easier for
> people to think in their own locale.
> Better to calculate than they have to think about the difference.
> If the user story is one where they would actively think in Gregorian UTC,
> then it could be reasonable to do what you’re doing.
I think this is the case here.
The app performs financial calculations that are valid in one timezone.
If the user locates to a different timezone the apps calculations must still
reference the initial timezone.
Failure to do this causes miscalculation.
> There are lots of conveniences added in the 10.9 SDK for calendrical
> calculation, and in general, it is easier for all to work in
> NSDate/NSTimeInterval (time since reference date) for calculation and then
> use locales for presentation.
> In this case you might consider the DB to be another user of sorts that needs
> its locale to be Gregorian UTC, so your work all happens in the intermediary
> form and humans and the DB get the locale they like to use.
> If you have the calendar and time zone, the dates are easier to covert to the
> non-locale form and that is easy to convert to any locale. (and vice versa).
> Or did I misunderstand something?
I don’t think so.
I was running into problems using the local locale (which utilises british
summer time) when computing the number of days between dates (I use the
NSCalendar category method shown below).
I suppose the question is equivalent to asking if it is possible to configure
an individual app to return a predefined NSCalendar instance for [NSCalendar
currentCalendar] (I severely doubt this is possible).
This would prevent me from introducing bugs by forgetting to configure my
NSDatePicker s correctly etc.
Thanks
Jonathan
- (NSInteger)daysWithinEraFromDate:(NSDate *) startDate toDate:(NSDate *)
endDate
{
NSInteger startDay=[self ordinalityOfUnit:NSDayCalendarUnit
inUnit: NSEraCalendarUnit
forDate:startDate];
NSInteger endDay=[self ordinalityOfUnit:NSDayCalendarUnit
inUnit: NSEraCalendarUnit forDate:endDate];
// note call ABS() for absolute difference
return endDay-startDay;
}
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