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Number   :  3499
Date     :  2003-01-10
Author   :  Kan Yabumoto
Subject  :  Re: Selecting files by date !
Size(KB) :  2



As far as XXCOPY is concerned, the only sensible date format
is yyyy-mm-dd. All other formats are ambiguous and we hope
the users will follow our strong recommendation that you
stick to this ISO standard. It is the best from any angle
you look at it.

The common American way, mm-dd-yyyy is indistinguishable
to the European way for many date values that is therefore,
equally bad. When you make it mm-dd-yy, it makes even
worse (four digit year is always superior than two digit
version, and leading zero at the year field does not
make it less ambiguous in our opinion since the leading
zero are well accepted in front of the day and month value
as well).

Actually, XXCOPY tries to accommodate a lot of variations
in the date value. For example, any of the following
parameters are accepted.

/DA:2001-10-31
/DA:10-31-2001
/DA:31-10-2001
/DA:10-31-01 // unambiguous, valid only in US format

But, the following parameter are not good.

/DA:01-10-31 // worst: 2001-10-31, 2031-01-10, or 2031-10-01
/DA:31-10-01 // bad: could be 2001-10-31 or 2031-10-01

Consider that above value has the number 31, which is
rather a fair case for this discussion because 31 cannot
be a value for month. But, if we choose smaller number for
all three, it will be a pure confusion.

/DA:01-02-03 // This is plain silly.
/DA:01-02-2003 // only slightly better but pretty bad.


(Note that XXCOPY does not care how far away the year 2031
is from today. If a value can be a valid date value for
year 2031, it is still ambiguous.)


The real culprit in your command was the fact you chose
the worst separator character for the date value.
That is, the slash character (/) which happens to be the
standard prefix for XXCOPY's command switch (and also
the starting character of a macro reference) is in
some context indistinguishable to the prefix of the
next command switch. XXCOPY accepts the hyphen (-)
character as the best date separator to use and it
also accepts the dot (.) which is European's favorite.
The slash character is the worst in the context of
XXCOPY command line.

Kan Yabumoto
=======================================================

At 2003-01-09 17:08, you wrote:
>I am having a problem with the date function (DA) on my Windows 98
>system with the current xxcopy.
>It fails if I use 01/01/2000 format even though this is the way the
>DOS date displays. When I enter /DA:2000 the oldest file copied is
>dated 6/4/02. Copy date is 01/09/2003. I am trying to copy all the
>files in the windows folder dated 1999 and later. Can you help me?
>BOB



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