Isn't midnight represented as 00:00?

Jim

news:19991102195609.11074.00000278@ng-cq1.aol.com...

How does your program know that the end time is a different date than the
start time?

Jim

news:19991102202218.02662.00000327@ng-cq1.aol.com...

I am entering simple data on a form using BegTime and EndTime fields.  All was
fine until I needed to enter 24:00 for midnight.  I can enter 23:59, but NOT
24:00.  I get the error message "The value you entered isn't valid for this
field."

I have the field in the table and the form formatted for Short Time.

Can anyone help me?

Thanks so much.  -Kathy

I've apparently never needed to use it before, and always thought of it as 24
of 24 hours...

I just tried it, but I'm using a DateDiff expression of
([EndTime]-[StartTime])/60 to come up with the number of hours/mins between the
two times.  Was working except using 00:00 - 22:00 gives me -22 hours.  Any
thoughts?  Thanks again.  I really appreciate the help...sometimes I just have
a brainfade or something...

I'm just using Short Time format so I only need to enter 06:30, 08:00, 17:30,
etc.

I've tried writing an expression to evaluate if EndTime = 0, then do something
else to BACK INTO the answer, but haven't got the math right yet.

Am I really missing the point here?  Someone suggested making it a Date and
Time field, but the user really just wants to have to enter the 00:00 format.
This one is giving me a headache.

Thanks for the help...Kathy

You can enter the time only, but Access will default the date part to 30 Dec
1899. If I remember rightly (the original question has been snipped) I think
the problem was getting the difference between two times that spanned
midnight? Here's an example in SQL (quick and dirty example, not necessarily
the most efficient way to do it, please treat as for illustration purposes
only!)

SELECT tblTest.TestTime1, tblTest.TestTime2,
(DateDiff("h",[TestTime1],[TestTime2])) AS Diff,
IIf([Diff]<0,[Diff]+24,[Diff]) AS Adjusted
FROM tblTest;

--
Brendan Reynolds
brenr...@indigo.ie
http://www.fortunecity.com/skyscraper/susumi/433/

news:19991103070158.02639.00000855@ng-cl1.aol.com...

I think your confusion is in thinking that midnight tonight is part of
today.  It isn't... midnight tonight is tomorrow, and midnight today was
this morning.

Simple solution is to check if time1 is less than time2.... and
if it is then adding a "day" in code by adding 1 to the number.

The Access date/time field is really not designed with elapsed
time in mind, its designed with date/time values in mind.

--
MichKa

-------------------------------------
don't send questions by e-mail unless
you're paying for it. (TANSTAAFL!) :-)

random junk of dubious value, replica
error and problem fixing, and the
*TSI Form/Report to Data Access Page Wizard*, at:
http://www.trigeminal.com

news:19991102202218.02662.00000327@ng-cq1.aol.com...
hours/mins between the
help...sometimes I just have

If 00:00 is the beginning of tomorrow and 24:00 is the end of today then
clearly they are the same time (00:00 = 24:00) else there would be some time
between them which was of neither today or tomorrow.

It's probably Time for me to Shut Up!

--
Lyle
http://www.cyriv.com/

jw...@tyenet.com (JWild) wrote in
<w2YT3.75926$y45.956...@news4.giganews.com>:

Sorry Lyle, but there is no such time as 24:00.  The end of today is
23:59:59.  The next second 0:00:00 is the beginning of tomorrow which is
considered midnight.
Try this in the debug window
IsDate("23:59")
True
IsDate("24:00")
False

<8E73781DClylefaircgocable...@24.226.64.57>...

I suppose from Access's point of view there is no 24:00:00. But from the
point of view of the International System of Measurement and of Logic there
is, and it is the same time as 00:00:00. I think this may help in
understanding why Access's arithmetic with hours and minutes is a tad
confusing at times, which is why I posted.

As far as the end of the day being 23:59:59,
where is 23:59:59.2?

Yes, I know, Access does not display anything greater than 23:59:59. The
reason it doesn't have to is simple; 24:00:00 and 00:00:00 are the same
times. Access has arbitrarily decided to include that time in the"next" day,
when, in fact, it is part of both today and tomorrow. But since the point in
time is infinitely small, it exists only as an idea.There is no actual
manifestation of any time. We can deal with times only as things we are
before, or things that we are after; we are never THERE in any static way,
but we pass THERE! (Xeno's Paradox).

AND

Sub test()

    Dim dtm1 As Date, dtm2 As Date

    dtm1 = (23& * 60& * 60& + 59& * 60& + 59!) / (24& * 60& * 60&)
    dtm2 = (23& * 60& * 60& + 59& * 60& + 59.2!) / (24& * 60& * 60&)

    Debug.Print dtm1    ' ... 11:59:59 PM
    Debug.Print dtm2    ' ... 11:59:59 PM
    Debug.Print (dtm1 = dtm2) '... False

End Sub

--
Lyle
http://www.cyriv.com/

news:%31U3.49081$7I4.956088@news5.giganews.com...

And that is really all that matters, I think, in the context of the original
post.

How can an organization with "logic" in its name allow midnight to be both
00:00 and 24:00?  It is illogical.

Jim

news:s21fjfsc24258@news.supernews.com...

Problem solved.  I added 1 day to the equation and that worked.  In this case,
the actual Date is moot, this is simply to calculate a billable hours number
for each time segment throughout the day...

Thanks to all...I was getting a little scared there when you took a turn to
24:00, no 24:00 - but interesting....KB

I trundled over to the second manual site, also known as Dev's Website
and looked at the help there on times:

if your times are likely to cross midnight then use the midnight
operator (-1)

But Datediff can be a clumsy way to find the  difference between two
times: try

dt=#00:00#
dt1=#22:00#
?format(dt-1-dt1,"short time")
22:00

or
dt=#01.30#
?hour(dt-1-dt1)
 20
?minute(dt-1-dt1)
 30

And if you want the whole lot tidier and in minutes

dt2=dt-1-dt1
?hour(dt2)*60+minute(dt2)
 1230

of course if your timespans should be longer than 24 hours then you
will have to either use logic or dates

Have Fun
Robin

On 03 Nov 1999 01:22:18 GMT, kathy...@aol.com (KathyB41) wrote:

That is total bunk, Chuck.

--
Lyle
http://www.cyriv.com/

c dot grimsby at worldnet dot att dot net (Chuck Grimsby)
wrote in <WPohOHakBN1jCMOmtggBKHY1G...@4ax.com>:

Lyle, actually its not bunk, Chuck is right.

I suggest that you either

(a) pull up a source for your claim that Access is somehow
violating a standard from the "International System of
Measurement and of Logic" [sic], or

(b) make good on your offer to shut up about it now.

You are misleading folks with your answers at this point.....
which is usually the point where (b) should be happening -- in
fact I was overjoyed when you volunteered to do so, in these
circumstances.

--
MichKa

-------------------------------------
don't send questions by e-mail unless
you're paying for it. (TANSTAAFL!) :-)

random junk of dubious value, replica
error and problem fixing, and the
*TSI Form/Report to Data Access Page Wizard*, at:
http://www.trigeminal.com

news:8E74E1127lylefaircgocablenet@24.226.64.57...

Michael

http://www.cl.cam.ac.uk/~mgk25/iso-time.html

A Summary of the International Standard Date and Time Notation
by Markus Kuhn

...

As every day both starts and ends with midnight, the two notations 00:00 and
24:00 are available to distinguish the two midnights that can be associated
with one date. This means that the following two notations refer to exactly the
same point in time:

1995-02-04 24:00 = 1995-02-05 00:00

....

--
Lyle
http://www.cyriv.com/

orignal_former_...@spamless.trigeminal.spamless.com (Michael (michka) Kaplan)
wrote in <#Kqn##4J$GA.267@cpmsnbbsa03>:

From ISO 8601: 1988 (E)

Date elements and interchange formats -
Information interchange - Reperesentation of dates and times

5.3.2 Midnight

The complete and extended representations for midnight , in accordance with
5.3.1, shall be expressed in either of the two following ways:

Basic format            Extended format
a) 000000               00:00:00 (the beginning of a day);
b) 240000               24:00:00 (the end of a day)

...

NOTES

1 Midnight will normally be represented as [0000] or [2400]

2 The choice of representation a) or b) will depend upon any assocation with a
date, or a time period.

3 The end of one day (2400) coincides with (0000) at the start of the next day,
e.g. 2400 on 12 April 1985 is the same as 0000 on 13 April 1985. If there is no
assoication with a date or a time period both a) and b) represent the same
clock time in the 24-hour timekeeping system.

**********

This document can be seen and printed (pdf) at
http://www.iso.ch/markete/8601.pdf

I recommend it for anyone who might have some interest in the topic.

--
Lyle
http://www.cyriv.com/

orignal_former_...@spamless.trigeminal.spamless.com (Michael (michka) Kaplan)
wrote in <#Kqn##4J$GA.267@cpmsnbbsa03>:

http://www.cl.cam.ac.uk/~mgk25/iso-time.html
http://www.iso.ch/markete/8601.pdf

Print out the documents and read them.

--
Lyle
http://www.cyriv.com/

c dot grimsby at worldnet dot att dot net (Chuck Grimsby)
wrote in <rzYjOFhTduQ7cN1DJJrV6EfYZ...@4ax.com>:

I went to:

http://tycho.usno.navy.mil/search.html

but could find nothing that addresses this issue. In any case I'm unwilling to
accept the authority of an institution renowned for lieing, (not to mention,
bullying) such as the US Navy. Oh wait, that explains it; I see what you mean
now. If I don't agree you'll get them to anchor a nuclear carrier in Lake
Ontario and bomb, strafe and rocket attack my community. Will this include
napalm for the kids, Chuck? Is that it?

So, since you didn't quote any authorities of your own, I guess I have to
choose between believing you or ISO and Markus. Who is Markus (the person who
wrote:"As every day both starts and ends with midnight, the two notations 00:00
and 24:00 are available to distinguish the two midnights that can be associated
with one date. This means that the following two notations refer to exactly the
same point in time:1995-02-04 24:00 = 1995-02-05 00:00"?

Funny, you should ask. This is straight from Markus's web site:

"Welcome!

My name is Markus Günther Kuhn (rhymes with moon) and I was born 1971-01-01 in
Munich, Germany. I grew up in Munich and later Uttenreuth near Erlangen (that
is here on a map), Germany. I received a graduate degree in Computer Science
(Dipl.-Inf.) at the University of Erlangen in July 1996. Subsequently, I spent
one year in the U.S. at Purdue University (Fulbright scholarship), where I did
some computer security reseach and received the Master's degree in August 1997.
Since October 1997, I have been working on a Ph.D. project in the Security
Group at the Computer Laboratory of the University of Cambridge in England
(Marie Curie scholarship). Eventually, I would like to teach and research at a
university or develop tricky high-tech systems somewhere on this planet.

My scientific interests include:

Computer Security, Hardware Security, Cryptology, Steganography, Intellectual
Property Protection Technology
Global-Scale Distributed Databases, Joint Administration, Digital Libraries,
SGML
Communication Systems, Computer Networks
Operating Systems, Linux
Digital Signal Processing, Advanced Video and Audio Technology, Data
Compression
International Standardization
Embedded Systems
Neural Physiology
Some of my special skills and fields of knowledge include pay-TV conditional
access systems, compromising emanations (Tempest), VLSI reverse engineering,
tamper resistance, smartcard systems, analyzing security systems, UNIX system
administration, POSIX/C/Ada system programming, textual-image compression, bus-
encryption processors, high precision timekeeping, timezone and calendar
algorithms, real-time programming, information and coding theory, modem
technology, character sets, Unicode, microcontrollers, efficient algorithms and
data structures, neural networks, and a few other topics about which I publish
and provide consultancy services occasionally.

Apart from this stuff, I enjoy bike riding, juggling, dancing, CCD astronomy,
USENET, BBC Radio 4, Apfelsaftschorle, unsolved problems, discussions with
interesting people, and torturing innocent pianos.

How you can contact me
Markus G. Kuhn
University of Cambridge
Computer Laboratory, TG1
New Museums Site, Pembroke Street
Cambridge CB2 3QG
United Kingdom
Phone:  +44 1223 3-34676
Fax:    +44 1223 3-34678
Email:  Markus.K...@cl.cam.ac.uk
        mg...@cam.ac.uk           (forwarded)
        mk...@acm.org             (forwarded)

At the moment, I am quite busy with various interesting projects. In addition,
my electronic mailbox is quite overcrowded. Therefore, please do not be angry
if I do not have the time to answer your mail. If your message was urgent, then
write again if I do not answer within a few days. Also please make sure that
your email return address is really reachable when you expect a reply from me.
And please do not try to contact me with Unix talk, better use email.

Secure email: For confidential messages, use PGP 2.6.3i and encrypt the email
with my public key. This key is changed occasionally, but it and and all future
of my public keys are signed with my high-security signing key (HSK)
(fingerprint F0 49 0D 10 F0 FA F6 5B E7 BC 78 54 5F 6E 46 2E, length 1024 bit).

If you want to send me files: Please do not send me proprietary word processor
files (FrameMaker, StarOffice, WordPerfect, Word, etc.). I prefer texts in
plain ASCII, ISO 8859-1, UTF-8, PDF, PostScript, HTML, TeX, and MIME, as well
as files packed with tar, gzip, uuencode, pkzip, and everything else for which
tools are freely available as open source code for POSIX systems such as Linux.
I do not use any Microsoft operating system.

Digital Publications
If you want to read any of the PDF files below, please make sure first that you
have Adobe Acrobat Reader 3.01 or newer installed. Please do not copy any of my
publications onto your own Internet server for public access without explicit
permission. If you want to refer to any of my texts, please use a hyperlink to
my original and not a copy. I update these texts frequently and and I want to
prevent the confusion that arises if people read somewhere else obsolete
versions that are not under my control.

English texts
Design Principles for Tamper-Resistant Smartcard Processors appeared in the
USENIX Workshop on Smartcard Technology proceedings, Chicago, Illinois, USA,
May 10-11, 1999 (slides) and describes a broad range of techniques to
compromise the security of smartcards and discusses countermeasures.
Soft Tempest: Hidden Data Transmission Using Electromagnetic Emanations,
appeared in David Aucsmith (Ed.): Information Hiding, Second International
Workshop, IH'98, Portland, Oregon, USA, April 15-17, 1998, Proceedings, LNCS
1525, Springer-Verlag, ISBN 3-540-65386-4, pp. 124-142. This paper presents a
few interesting new twists on eavesdropping computers using their compromising
electromagnetic emanations as well as some software protection techniques
(slides).
Tamper Resistance - a Cautionary Note appeared in The Second USENIX Workshop on
Electronic Commerce Proceedings, Oakland, California, November 18-21, 1996, pp
1-11 (PDF version, slides, presentation notes) and is an early describtion of
attack techniques on smartcards and other security processors.
Low Cost Attacks on Tamper Resistant Devices appeared in M Lomas et al. (ed.),
Security Protocols, 5th International Workshop, Paris, France, April 7-9, 1997,
Proceedings, Springer LNCS 1361, pp 125-136, ISBN 3-540-64040-1.
Probability Theory for Pickpockets - ec-PIN Guessing was a talk I gave at the
DREI'97 workshop at Ruttgers University, New Jersey, to an audience of high
school math teachers to demonstrate how probability theory is important for the
design of secure computer applications. The text describes a now well-known
weakness in the PIN algorithm used with German EuroCheque cards and was later
reprinted in Datenschleuder.
Attacks on Pay-TV Access Control Systems was a talk that I presented 1997-12-09
in the Cambridge Security Seminar (slides only).
Analysis of a Denial of Service Attack on TCP, Proceedings IEEE Symposium on
Security and Privacy 1997, Oakland, California.
The TrustNo1 Cryptoprocessor Concept, CS555 Report, Purdue University, April
1997 gives an idea of how the software copy protection of the future could look
like.
Standards FAQ, posted periodically to USENET groups comp.std.misc and
news.answers. This text summarizes useful information about international
technical standards (ISO, ITU, ECMA, etc.). For related information, you might
also want to have a look at the anonymous ftp server archive
ftp://ftp.informatik.uni-erlangen.de/pub/doc/ISO/. I also wrote the
comp.protocols.iso FAQ with some information about OSI protocols a few years
ago. These texts are not very up-to-date at the moment.
Specification of the EBS File Format for Bio-Signals. A proposal for a standard
computer file format suitable for recording, processing and archiving of
biological and medical signals (e.g. ECG, EEG, MEG, etc.). For more information
and public domain software, please check our ftp archive ftp://ftp.uni-
erlangen.de/pub/ebs/.
International Standard Date and Time Notation is a brief introduction into the
ISO 8601 standard. If you have never heard about this standard before, you
definitely should read this text. There is also a description of International
Standard Paper Sizes, i.e. formats like A4, which are used today everywhere
outside North America. I wrote this text in the hope to convince folks in the
U.S. to give up their strange paper formats, which only cause headaches all
over the planet for users of word processors, laser printers, and copying
machines. There is also a new text about metric font sizes.
Standardized Units for Use in Information Technology is my proposal for a
formal international standard that would finally provide an authoritative
answer to questions like "How many bytes are there in a megabyte?" and "What is
the correct symbol for kilobyte?". Discussion is welcome.
A survey of POSIX.1b Compatibility and Real-Time Support in the Linux operating
system.
A brief summary of the Digital Video Broadcast (DVB) Standard, which specifies
the digital TV broadcasting technology that is currently being introduced in
many countries.
There is also a text about the new EU directive on the legal protection of
encrypted services, against earlier drafts of which I did some lobbying (with
success it seems).
Information for New Ada95 Programmers summarizes useful information I came
across when I started to learn what I now consider to be a very good large-
systems programming language. See also the Ada for Linux Team Page.
Effective Scientific Electronic Publishing contains a number of tips for
preparing online papers, mostly intended for our local research group, but
probably useful for others as well who want to generate nice PDF files with
LaTeX. ...

read more »

Comments below:

c dot grimsby at worldnet dot att dot net (Chuck Grimsby)
wrote in <oOMlOMPMDnX9eElj63NF4hKoj...@4ax.com>:

One of the most disappointing things in the recent wars in this group is the
arrogance of a few regulars whose attitude is, "Believe as we believe, or we
shall banish you unto everlasting darkness." I think it MAY have been I, myself
who started the current "plonk" craze, and it's something I regret. The idea
that some people in this group have such a lock on knowledge about Access that
they should be able to throw their weight around in that fashion is ludicrous
and is a manifestation of great arrogance, or maybe great insecurity.

Yes, to all of the above.

Ditto

We specified early in the thread that MS used only 00:00 to designate midnight.
The first post in the thread shows how useful it would be were they to
introduce 24:00 to indicate midnight as the final point of time in a day, while
using 00:00 to indicate the first point of time in a day.

Without 24:00 we have no point where the day ends. For between every two
distinct points in time there is another point.
If today ends at 23:59:59 what day is 23:59:59.5 in?
Only if a day ends at the same point that the next one begins can we have a
logical last point in time of the day.

I believe someone wanted me to "pull up a source". Unfortunately, since he is
Never_Wrong he ignored the several which I provided, as you, apparently, are
doing as well. The only difference is that your action surprises me.

It's OK to be wrong; I have been many times, but this isn't one of them.

--
Lyle
http://www.cyriv.com/

Fair enough.

c dot grimsby at worldnet dot att dot net (Chuck Grimsby)
wrote in <vzknONdzLPZV0jLK5OYqBlskw...@4ax.com>:

--
Lyle
http://www.cyriv.com/

Hi,

Sorry: 23:59:60 is not 24:00:00 ( or 00:00:00), it is the sixty-first
second, used to designated a leap second (one occurs around each 500 days).
No database I know care about that leap second. Twenty-two leaps seconds
occurred since 1972, time at which that convention had been established. If
you "don't care" about that leap second, you may say 23:59:50 is 24:00:00,
but it is interesting to know some others "won't don't" care.

(There is a need to establish that correction because a second is define on
some period of caesium 133, something quite constant, and a day is defined
with respect to earth rotation, not constant, but decreasing (good news, the
moon is escaping, not going to crash on earth, but like an artist on ice,
the momentum has to stay constant, so, earth turn slower and slower...). So,
with 24 hours a days, 60 minutes an hour, the correction is done on the
60-61 seconds a minute).

Vanderghast, Access MVP.

news:8E78BD5Dlylefaircgocablenet@24.226.64.57...

Hello,

It has been interesting and educational watching this conversation.  I have
collated all ideas and was able to come up with an IIf function applicable
to my database.....getting the correct difference (not negative) between two
time.

I am doing a small A2K application to keep track of time usage of a certain
computer as well as keeping track of the day's sales.  However, I have come
to a stumbling block.  I couldn't get the IIf function results for all
records to be added so I can have a total. I keep getting this: #Error.

TimeUsed1 = DateDiff("n",[TimeIn],[TimeOut])
TimeUsed2 = IIf([TimeUsed1]<0,[TimeUsed1]+1440,[TimeUsed1])          '1440
being minutes in 24 hours

The end result that I would like to achieve is to get the total of
[TimeUsed2]. I believe that this can be achieved but I just don't have any
idea how to go about it.  I would appreciate any enlightenment. This group
has been very helpful.

Thanks,

Darl Rodriguez

Michael (michka) Kaplan

news:OFZ9AKhJ$GA.292@cpmsnbbsa02...