[AccessD] TimeSerial buggy for negative date values

I must have missed a step.  Why would you want to use negative date
values?  HOW would you want to use negative date values??

Charlotte Foust 

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Gustav Brock
Sent: Sunday, August 10, 2008 8:55 AM
To: accessd at databaseadvisors.com
Subject: Re: [AccessD] TimeSerial buggy for negative date values

Hi Jim

Thanks. 
I can add that I've searched all over for some comments to this. The
only writing I ever found was this (in German):

  http://www.vbarchiv.net/tipps/details.php?id=1308

which deals with a lot of stuff about datetime and specifically mentions
this "feature" of TimeSerial.

/gustav

>>> accessd at shaw.ca 10-08-2008 17:43 >>>
Great tip Gustav. 

Jim

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Gustav Brock
Sent: Sunday, August 10, 2008 5:06 AM
To: accessd at databaseadvisors.com
Subject: Re: [AccessD] TimeSerial buggy for negative date values

Hi all

I brushed this bug up and nothing has changed for Access 2007.

Also, I believe I can tell why TimeSerial has been designed this way.
The reason is that you with this behaviour can sum time values directly,
because it for negative inputs returns a symmetrical negative value from
time zero as this example demonstrates:


? TimeSerial(-18, 20, 0) + TimeSerial(18, -20, 0) 00:00:00 

But don't attempt to use DateDiff on these values:

? DateDiff("n", TimeSerial(-18, 20, 0), TimeSerial(18, -20, 0))
 1 

If you need to use DateDiff - which normally is the recommended method
by Microsoft - use my TimeSerialFull or similar:

? DateDiff("n", TimeSerialFull(-18, 20, 0), TimeSerialFull(18, -20, 0))
2120 

but, of course, don't attempt to add the values of TimeSerialFull
directly:

? TimeSerialFull(-18, 20, 0) + TimeSerialFull(18, -20, 0) 12:40:00 

To conclude, this is probably a bug by intention but the documentation
doesn't describe or explain this with a single word.

/gustav



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