one thing though... how can Delphi and IB not have the same starting point?
Surely the date values will be different for each starting point?

Alan
-----Original Message-----
From: Helen Borrie [mailto:helebor@...]
Sent: Thursday, 31 October 2002 15:16
To: ib-support@yahoogroups.com
Subject: RE: [ib-support] Date Format in IB


At 05:26 PM 30-10-02 -0500, you wrote:

>At 08:53 AM 10/31/2002 +1100, Alan McDonald wrote:
> >Ann,
> >Has this changed sometime?

Ann wrote:

>No, but what we're seeing are conversions done in
>the interface. Dates can be converted to floating
>point - that's how they're indexed, as it happens.
>I don't know whether it was InterBase or Delphi that
>did the conversion, but the InterBase internal format
>is two longwords.
>
> >Also I used to see "zero" dates come up in reports as 31 Dec 1899 -

when

> did this starting point change?

It hasn't changed in all the time I've been using Delphi and/or
InterBase. Delphi's date zero has always been (I think) 30 Dec 1899 and
IB's was always 17 Nov 1858. Although Delphi dates are doubles, not a
packed structure like IB's, it can still be convenient to think of them as
two time-lines each looking at the "catchment of possible dates" in
similar
ways but from two different starting blocks.

Ann wrote:

>Ah. Whatever you were using went through the date
>conversion routines. They use the Unix/C tm structure
>which is uses Jan 1 1900 as its base date. It's a
>wonderful thing. Doesn't recognize anything smaller
>than a second. Months are zero based. Days are one
>based. So year 0, month 0, day 1 is 1 Jan 1900.
>Year 0, month 0, day 0 must be one day less, so...
>31 Dec 1899.

Just as a matter of interest (in the course of trying to refresh my memory
about Delphi's zero-date being 30 Dec 1899 and not 31 Dec 1899) I
attempted
this little experiment on a Dialect 3 database:

CREATE TABLE TEST_DATE (
ID INTEGER NOT NULL PRIMARY KEY,
DATE1 TIMESTAMP,
DATE2 DATE);

commit;

insert into test_date
values (101, cast ('today' as timestamp),
cast (current_date - current_date as date);

The above (and everything else) came up every time with this or a similar
error, not at Prepare time but at Post time:

ISC ERROR CODE:335544334

ISC ERROR MESSAGE:
conversion error from string "0"

...and various other ploys to get Fb to accept zero as a date, e.g.

insert into test_date
values (101, cast (current_timestamp - current_timestamp as timestamp),
current_date)

ISC ERROR CODE:335544334

ISC ERROR MESSAGE:
conversion error from string "0.000000000"

It accepts '1858-11-17' as a date literal and Delphi happily displays it
(from the database) as that date.

It's interesting because, IIR, in lower versions, IB would allow you to
store a number 0, a string literal '0' or the result of an expression like
the one above.
It might or might not be the outcome of any changes in either Delphi or IB
though, since my recollections of IB 4.x go back to the days when I used
the BDE and it's quite likely the BDE did the "fudge" that permitted
storage of zero in a (then) date-time DATE field.

Oh, and I still haven't confirmed whether my recollection of Delphi's zero
date was wrong or not...these days I don't have either IB 4.x or the BDE
around my systems at all so it will just have to stay being a "niggle".

cheers,
heLen


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