dhis2-devs team mailing list archive

[Bob Jolliffe <bobjolliffe@xxxxxxxxx>]

On 13 April 2013 13:26, Saptarshi Purkayastha <sunbiz@xxxxxxxxx> wrote:

> I think we should be Calendar agnostic in code and like most i18n capable
> systems, not expect the timestamp in the database to be Calendar-specific
> Postgres for instance uses Julian calendar internally. But still supports
> many different systems, much more than standard SQL asks for.
> Java similar uses long values, instead of Calendar-specific
> representations.
>
> My point is, Java, Postgres (and MySQL) are well designed to work by being
> calendar-agnostic.
> Also, Joda-time<http://joda-time.sourceforge.net/apidocs/org/joda/time/chrono/package-summary.html>provides nice Chronology classes for different calendars, which we can use
> for localized storing, retrieving or converting
>

Am I right in thinking joda-time is now integrated into the java.time
package of java 8?


>
> For the JavaME app in one of the releases, we did have a custom calendar
> component.
> Having it display BS, Ethiopian or anything else, should be fairly easy.
> But yes, very few low-end Java phones are locale specific.
>
>
> ---
> Regards,
> Saptarshi PURKAYASTHA
>
> My Tech Blog:  http://sunnytalkstech.blogspot.com
> You Live by CHOICE, Not by CHANCE
>
>
> On 13 April 2013 10:36, Jason Pickering <jason.p.pickering@xxxxxxxxx>wrote:
>
>> Hi Saptarshi,
>> Yes, I  cannot speculate really why DHIS2 only supports the Gregorian
>> calendar, but this issue I think has been discussed a few times on the list
>> before (perhaps for other countries).
>>
>> I feel the best approach would be to store all of the data with Gregorian
>> dates, but what is shown through the web UI would be the calendar system of
>> the particular instance. I am not even sure if databases like Postgres and
>> MySQL (much less the operating system itself) would support non Gregorian
>> calendar systems.
>>
>> As for data exchange, I see no immediate need for this, but if data is
>> stored in Gregorian format ( I suppose the de facto international
>> standard), then perhaps data exchange would be somewhat easier, but this is
>> just speculation of course.
>>
>> Thanks for the link to the BS date picker. Does not seem to difficult to
>> solve at least this problem.The bigger issue as I see it would be data
>> entry through mobiles. At least the J2ME app uses the system calendar, and
>> do not think that non-Gregorian systems are even supported on any phone?
>>
>> Best regards,
>> Jason
>>
>>
>>
>>
>>
>> On Fri, Apr 12, 2013 at 5:16 PM, Saptarshi Purkayastha <sunbiz@xxxxxxxxx>wrote:
>>
>>> Hi Jason,
>>>
>>> When you say the system currently only support Gregorian calendar, I
>>> wonder if that's a fact of JavaScript widgets
>>> But while I was writing this email, a quick search in the code base
>>> shows that we've instantiated Gregorian calendar at many places instead of
>>> using the more localized Calendar.getInstance(). The first task would be
>>> move to using this
>>>
>>> Secondly, is conversion between Gregorian dates and some other calendar
>>> really required. If data is exchanged between different systems with
>>> different calendars, this is important. But if we are storing a timestamp
>>> in database, it should be fine to store it in the locale calendar. So I am
>>> not too keen, unless really required to use the maps that allow co-relating
>>> dates between calendar systems.
>>>
>>> Thirdly, there are quite a few (and fairly easy to write new JavaScript
>>> calendars) to suite different locales. The care that we need to take is
>>> being able to retrieve the correct calendar based on the set locale. A
>>> simple BS calendar JS -
>>> http://sajanmaharjan.com.np/my-works/nepali-datepicker-ui/
>>>
>>> ---
>>> Regards,
>>> Saptarshi PURKAYASTHA
>>>
>>> My Tech Blog:  http://sunnytalkstech.blogspot.com
>>> You Live by CHOICE, Not by CHANCE
>>>
>>>
>>> On 12 April 2013 12:56, Jason Pickering <jason.p.pickering@xxxxxxxxx>wrote:
>>>
>>>> Hi Devs,
>>>> I have a question regarding non-Gregorian (Western) calendar systems.
>>>> This issue has come up in a couple of different places which I know of,
>>>> namely Ethiopia (Ethiopian calendar) and Afghanistan (Solar Hijri
>>>> calendar). Currently, the system only supports a Gregorian calendar system,
>>>> but I am trying to think of ways how we can support different
>>>> ones, specifically the Bikram Sambat (BS) calendar system used in Nepal.
>>>>
>>>>
>>>> There appears to be no easy way to convert between a Gregorian
>>>> calendar. I dug out some code here
>>>> <https://github.com/bahadurbaniya/Date-Converter-Bikram-Sambat-to-English-Date> which
>>>> will convert between Gregorian dates and BS dates (but not the other way
>>>> around). The approach is to use a look-up table, because of the fact that
>>>> it seems to be difficult (if not impossible) to calculate the
>>>> conversion algorithmically.
>>>>
>>>> This leads me to my question. Would it be possible that we consider
>>>> adding a "Calendar system" to the application. The default would be
>>>> "Gregorian", which is currently the case. The Second alternative might be
>>>> "Bikram Sambat". This would require someone to prepopulate the system with
>>>> periods (BS months, quarters and years)   which would be calculated through
>>>> some other means (common Lisp code here<http://emr.cs.uiuc.edu/~reingold/calendar.l> which
>>>> may be able to do this). These would be in Gregorian periods, but instead
>>>> of the system calculating future periods, they would have to be
>>>> pre-calculated and entered/imported into the system somehow.
>>>>
>>>> The second part of this (which I think may be more difficult) is the
>>>> use of the JavaScript Gregorian calendar throughout the system. For data
>>>> entry of aggregate data, it would not to be too problematic. But for the
>>>> tracker module (and other places in the system), a Gregorian Javascript
>>>> widget is used, and it would seem to be potentially difficult to replace
>>>> this.
>>>>
>>>> Could the developers comment on feasibility and possible level of
>>>> effort?
>>>>
>>>> Best regards,
>>>> Jason
>>>>
>>>>
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>>>>
>>>
>>
>
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