[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