Re: dateWithCalendarFormat: problem?

FROM : Nick Zitzmann
DATE : Fri Feb 15 21:43:47 2008

On Feb 15, 2008 AD, at 1:13 AM, norio wrote:

> If I typed "0" in the year part then typed 'tab', the DatePicker 
> displayed 0001/02/13.
> Isn't it correct? I thought I would be 0000/02/13.



NSDatePicker is correct. There is no year 0 on the Gregorian calendar; 
the people who designed the Julian calendar thousands of years ago 
didn't have any concept of the number 0. Incidentally, there is no 
year 0 in any other calendar type.

> However if I pressed the button to convert it into NSCalendarDate 
> using dateWithCalendarFormat:timeZone:, the text field displayed 
> '-2007-01-27 01:00:00 +0900'.
> NSLog showed the following.
> 2008-02-15 16:57:56.080 datepicker[1141:813] 2008-02-13 01:00:00 +0900
>
> Would you tell me what I'm missing?


I think you somehow got NSDatePicker to go into the BC era, probably 
by entering the year 0 beforehand. There's a subtle difference between 
using NSCalendar/NSDate and NSCalendarDate to calculate date 
components; NSCalendarDate assumes use of the Gregorian calendar 
forever, whereas NSCalendar/NSDate starts using the Julian calendar 
for dates prior to October 15, 1582 AD. That would explain the date 
discrepancy.

Nick Zitzmann
<http://www.chronosnet.com/>