Re: [Pharo-users] adding 1 year to the date - bug?

[Richard O'Keefe]

It makes sense to add a Duration to a DateAndTime.
It does not make sense to add a Duration to a Date.
I can't check Pharo because I haven't managed to
get it working on this laptop (x86-64 + ubuntu 17),
but Squeak has Date>>addMonths: (edited for clarity):

addMonths: monthCount
|m year month maxDaysInMonth day|
m := monthCount + self monthIndex - 1.
year := m // 12 + self year.
month := m \\ 12 + 1.
maxDaysInMonth := Month daysInMonth: month forYear: year.
day := self dayOfMonth min: maxDaysInMonth.
^ Date
newDay: day
month: month
year: year

This may or may not do what your customer wants.

On 26 February 2018 at 22:43, Petr Fischer  wrote:

> Hello, just simple test:
>
> (Date year: 2019 month: 2 day: 26) + 1 year.
> returns: 26 February 2020
> OK
>
> (Date year: 2020 month: 2 day: 26) + 1 year.
> returns: 25 February 2021
> What?
>
> (maybe I do not understand something  about dates again)
>
> Thanks! pf
>
>

Re: [Pharo-users] adding 1 year to the date - bug?

[Petr Fischer]

Thanks for discussion thread link. And yes, I need to implement it myself for 
customer needs, especially things like:

January 31 + 1 month = February 28/29
February 29 + 1 year = February 28
etc. :)

pf

> This is a discussion we already had years ago. And comes back every once in
> a while.
> 
> Pharo, and all dialects to my knowledge, uses incremental based
> calculations instead of field based calculations (like java.util.Calendar).
> 
> This is the best thread I remember where we discussed this.
> http://forum.world.st/Interesting-Date-Time-Thread-
> on-Squeak-Dev-td4778652.html#a4778970
> 
> 
> Regards,
> 
> --
> Esteban.
> 
> El feb. 26, 2018 7:33 AM, "jtuc...@objektfabrik.de" 
> escribió:
> 
> Am 26.02.18 um 11:13 schrieb Petr Fischer:
> 
> So "date addMonths: 12" behaves better for my needs. Thanks
> >
> Hmm. We've had this discussion just the other day at Lunch. What is a
> month? Should addMonths: 1 and then subtractMonths: 1 on January 31st bring
> you back to January 31st? How would you implement that?
> 
> I guess this is a problem that cannot be solved by a machine without
> additional context. Does 1 month later mean "on this day next month" or
> does it mean "exactly as many days in the future as the current month has
> days"? None of the two? Can one month later be in March when today is
> January 30th?
> 
> It seems years and months are a bit incompatible with informatics ;-) In my
> opinion, there is more info needed than "x months/years later" in order to
> calculate the correct result.
> 
> Joachim
> 
> 
> 
> 
> 
> 
> >
> > Hello, just simple test:
> >>
> >> (Date year: 2019 month: 2 day: 26) + 1 year.
> >> returns: 26 February 2020
> >> OK
> >>
> >> (Date year: 2020 month: 2 day: 26) + 1 year.
> >> returns: 25 February 2021
> >> What?
> >>
> >> (maybe I do not understand something  about dates again)
> >>
> >> Thanks! pf
> >>
> >>
> >
> -- 
> ---
> Objektfabrik Joachim Tuchel  mailto:jtuc...@objektfabrik.de
> Fliederweg 1 http://www.objektfabrik.de
> D-71640 Ludwigsburg  http://joachimtuchel.wordpress.com
> Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1

Re: [Pharo-users] adding 1 year to the date - bug?

[Esteban A. Maringolo]

This is a discussion we already had years ago. And comes back every once in
a while.

Pharo, and all dialects to my knowledge, uses incremental based
calculations instead of field based calculations (like java.util.Calendar).

This is the best thread I remember where we discussed this.
http://forum.world.st/Interesting-Date-Time-Thread-
on-Squeak-Dev-td4778652.html#a4778970


Regards,

--
Esteban.

El feb. 26, 2018 7:33 AM, "jtuc...@objektfabrik.de" 
escribió:

Am 26.02.18 um 11:13 schrieb Petr Fischer:

So "date addMonths: 12" behaves better for my needs. Thanks
>
Hmm. We've had this discussion just the other day at Lunch. What is a
month? Should addMonths: 1 and then subtractMonths: 1 on January 31st bring
you back to January 31st? How would you implement that?

I guess this is a problem that cannot be solved by a machine without
additional context. Does 1 month later mean "on this day next month" or
does it mean "exactly as many days in the future as the current month has
days"? None of the two? Can one month later be in March when today is
January 30th?

It seems years and months are a bit incompatible with informatics ;-) In my
opinion, there is more info needed than "x months/years later" in order to
calculate the correct result.

Joachim






>
> Hello, just simple test:
>>
>> (Date year: 2019 month: 2 day: 26) + 1 year.
>> returns: 26 February 2020
>> OK
>>
>> (Date year: 2020 month: 2 day: 26) + 1 year.
>> returns: 25 February 2021
>> What?
>>
>> (maybe I do not understand something  about dates again)
>>
>> Thanks! pf
>>
>>
>
-- 
---
Objektfabrik Joachim Tuchel  mailto:jtuc...@objektfabrik.de
Fliederweg 1 http://www.objektfabrik.de
D-71640 Ludwigsburg  http://joachimtuchel.wordpress.com
Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1

Re: [Pharo-users] adding 1 year to the date - bug?

[Sean P. DeNigris]

NorbertHartl wrote
> Forgot to say that this is something you can experience quite often. To me
> the problem is that 1 year gives a duration immediately. It should work as
> all units that 1 year is a unit of magnitude 1 and unit year. If you apply
> this to a date you could make it properly to give the date one year later.

Yes!!!



-
Cheers,
Sean
--
Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Re: [Pharo-users] adding 1 year to the date - bug?

[jtuc...@objektfabrik.de]

Am 26.02.18 um 11:13 schrieb Petr Fischer:

So "date addMonths: 12" behaves better for my needs. Thanks
Hmm. We've had this discussion just the other day at Lunch. What is a 
month? Should addMonths: 1 and then subtractMonths: 1 on January 31st 
bring you back to January 31st? How would you implement that?


I guess this is a problem that cannot be solved by a machine without 
additional context. Does 1 month later mean "on this day next month" or 
does it mean "exactly as many days in the future as the current month 
has days"? None of the two? Can one month later be in March when today 
is January 30th?


It seems years and months are a bit incompatible with informatics ;-) In 
my opinion, there is more info needed than "x months/years later" in 
order to calculate the correct result.


Joachim








Hello, just simple test:

(Date year: 2019 month: 2 day: 26) + 1 year.
returns: 26 February 2020
OK

(Date year: 2020 month: 2 day: 26) + 1 year.
returns: 25 February 2021
What?

(maybe I do not understand something  about dates again)

Thanks! pf





--
---
Objektfabrik Joachim Tuchel  mailto:jtuc...@objektfabrik.de
Fliederweg 1                         http://www.objektfabrik.de
D-71640 Ludwigsburg  http://joachimtuchel.wordpress.com
Telefon: +49 7141 56 10 86 0         Fax: +49 7141 56 10 86 1

Re: [Pharo-users] adding 1 year to the date - bug?

[Petr Fischer]

So "date addMonths: 12" behaves better for my needs. Thanks


> Hello, just simple test:
> 
> (Date year: 2019 month: 2 day: 26) + 1 year.
> returns: 26 February 2020
> OK
> 
> (Date year: 2020 month: 2 day: 26) + 1 year.
> returns: 25 February 2021
> What?
> 
> (maybe I do not understand something  about dates again)
> 
> Thanks! pf
> 

Re: [Pharo-users] adding 1 year to the date - bug?

[Tudor Girba]

+1

Doru


> On Feb 26, 2018, at 10:54 AM, Norbert Hartl  wrote:
> 
> Forgot to say that this is something you can experience quite often. To me 
> the problem is that 1 year gives a duration immediately. It should work as 
> all units that 1 year is a unit of magnitude 1 and unit year. If you apply 
> this to a date you could make it properly to give the date one year later. 
> I noticed that problem when I started to use the Units package of Marcus. It 
> works for all units except durations because these are already taken. So for 
> me there would be two benefits changing that. 
> 
> Norbert
> 
> 
>> Am 26.02.2018 um 10:48 schrieb Norbert Hartl :
>> 
>> 
>> 
>>> Am 26.02.2018 um 10:43 schrieb Petr Fischer :
>>> 
>>> Hello, just simple test:
>>> 
>>> (Date year: 2019 month: 2 day: 26) + 1 year.
>>> returns: 26 February 2020
>>> OK
>>> 
>>> (Date year: 2020 month: 2 day: 26) + 1 year.
>>> returns: 25 February 2021
>>> What?
>>> 
>>> (maybe I do not understand something  about dates again)
>> 
>> That is a conceptual problem. 1 year is a duration. As it does not know 
>> which year it is the normal 365 days. And 2020 is a leap year so has 366 
>> days. That’s why the date is shifted.
>> 
>> Norbert
> 

--
www.tudorgirba.com
www.feenk.com

"What we can governs what we wish."

Re: [Pharo-users] adding 1 year to the date - bug?

[Norbert Hartl]

Forgot to say that this is something you can experience quite often. To me the 
problem is that 1 year gives a duration immediately. It should work as all 
units that 1 year is a unit of magnitude 1 and unit year. If you apply this to 
a date you could make it properly to give the date one year later. 
I noticed that problem when I started to use the Units package of Marcus. It 
works for all units except durations because these are already taken. So for me 
there would be two benefits changing that. 

Norbert


> Am 26.02.2018 um 10:48 schrieb Norbert Hartl :
> 
> 
> 
>> Am 26.02.2018 um 10:43 schrieb Petr Fischer :
>> 
>> Hello, just simple test:
>> 
>> (Date year: 2019 month: 2 day: 26) + 1 year.
>> returns: 26 February 2020
>> OK
>> 
>> (Date year: 2020 month: 2 day: 26) + 1 year.
>> returns: 25 February 2021
>> What?
>> 
>> (maybe I do not understand something  about dates again)
> 
> That is a conceptual problem. 1 year is a duration. As it does not know which 
> year it is the normal 365 days. And 2020 is a leap year so has 366 days. 
> That’s why the date is shifted.
> 
> Norbert

Re: [Pharo-users] adding 1 year to the date - bug?

[Norbert Hartl]

> Am 26.02.2018 um 10:43 schrieb Petr Fischer :
> 
> Hello, just simple test:
> 
> (Date year: 2019 month: 2 day: 26) + 1 year.
> returns: 26 February 2020
> OK
> 
> (Date year: 2020 month: 2 day: 26) + 1 year.
> returns: 25 February 2021
> What?
> 
> (maybe I do not understand something  about dates again)

That is a conceptual problem. 1 year is a duration. As it does not know which 
year it is the normal 365 days. And 2020 is a leap year so has 366 days. That’s 
why the date is shifted.

Norbert

Re: [Pharo-users] adding 1 year to the date - bug?

[Pavel Krivanek]

In Pharo 1 year is a duration of 365 days so it does not reflect leap years.

-- Pavel

2018-02-26 10:43 GMT+01:00 Petr Fischer :
> Hello, just simple test:
>
> (Date year: 2019 month: 2 day: 26) + 1 year.
> returns: 26 February 2020
> OK
>
> (Date year: 2020 month: 2 day: 26) + 1 year.
> returns: 25 February 2021
> What?
>
> (maybe I do not understand something  about dates again)
>
> Thanks! pf
>

[Pharo-users] adding 1 year to the date - bug?

[Petr Fischer]

Hello, just simple test:

(Date year: 2019 month: 2 day: 26) + 1 year.
returns: 26 February 2020
OK

(Date year: 2020 month: 2 day: 26) + 1 year.
returns: 25 February 2021
What?

(maybe I do not understand something  about dates again)

Thanks! pf