Re: Mabye OT: Was Re: Different clocks for different instances.

Brian McGraw wrote:
>
> Speaking of the system clock, here's something interesting that I
> stumbled across a few years back...
>
> Background: For those of you who may not know, the Julian calendar
> was abandoned by England, in favor of the Gregorian calendar, in 1752
> because of date discrepancies. To facilitate this, September 3 - 13
> were eliminated. This is actually reflected in UNIX (well, Solaris
> anyway) by issuing the 'cal 1752' command and looking at the month of
> September:
>
> Jul Aug Sep
> S M Tu W Th F S S M Tu W Th F S S M Tu W Th F S
> 1 2 3 4 1 1 2 14 15 16
> 5 6 7 8 9 10 11 2 3 4 5 6 7 8 17 18 19 20 21 22 23
> 12 13 14 15 16 17 18 9 10 11 12 13 14 15 24 25 26 27 28 29 30
> 19 20 21 22 23 24 25 16 17 18 19 20 21 22
> 26 27 28 29 30 31 23 24 25 26 27 28 29
>
> More info. on why the switch over occurred is available at
> http://www.bicknell.net/books/pc1981/p_calender.htm, for those of you
> with morbid curiosity.
>
> Anyway - I was doing some Y2K testing a few years back, and playing
> with NLS_DATE_FORMAT queries when I learned this little tidbit. I
> decided to test the Oracle date formats because - hey - they'll be
> okay because they're based on Unix, right?
>
> Wrong: Issue the following query:
>
> select sysdate
> ,add_months(sysdate,-2988)
> ,add_months(sysdate,-2988) - 10
> from dual;
>
> And see the following results:
>
> SYSDATE ADD_MONTHS(SYSDATE,- ADD_MONTHS(SYSDATE,-
> -------------------- -------------------- --------------------
> 19-DEC-2001 10:07:02 19-DEC-1752 10:07:02 09-DEC-1752 10:07:02
>
> The third column represents a date which, technically, does not
> exist. : )
>
> Brian
>

Brian,

  Speak for yourself. The continent, much more enlightened, had switched in October 1582. England had opted out, as it seems, and jumped on the bandwagon belatedly (sounds furiously modern, doesn't it?). Check within Oracle the number of days in October 1582, you will see that it's correct (from my point of view). I don't think that you can say that the Oracle date is based on the system date for these dates, because Unix systems only see dark ages before 1st Jan 1970.

-- 
Regards,

Stephane Faroult
Oriole Ltd
-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Stephane Faroult
  INET: sfaroult_at_oriole.com

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