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
Kimberly Smith wrote:
Oracle uses the system clock. So I would have to say no.-------Original Message-----
Pollard
Sent: Tuesday, December 18, 2001 6:50 PM
To: Multiple recipients of list ORACLE-LGooday Oraclers,
is it possible to have different instances, on the same dB server,
operating with different clocks - ie different date/times?Environment: Compaq-Digital Tru64 Unix, Oracle 8.0.6, DS20
---
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Room: R1-40a | Lismore NSW 2480, Australia
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| Brian McGraw -- Oracle DBA |
| Central Alabama Oracle Users Group |
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