Perl and Y2K

[Tom Christiansen <tchrist@jhereg.perl.com>]

I wasn't going to say anything, but I guess this isn't common knowledge.
Here's the README.Y2K from the latest Perl release (_63).  Please pay
special attention to the -DPERL_Y2KWARN configuration option.  It
produces an effect like this:

    % perl -we 'printf "Year is 19%d\n", (localtime)[5]'
    Possible Y2K bug: %d format string following '19' at -e line 1.
    Year is 19100

Interesting, eh?  Another option is to use the
http://www.perl.com/CPAN/authors/Michael_G_Schwern/D-oh-Year-0.04.tar.gz
module.  The author writes about it here: 
http://www.deja.com/getdoc.xp?AN=542686902&fmt=text

Anyway, here's the README.Y2K from _63:

--tom


    The following information about Perl and the year 2000 is a modified
    version of the information that can be found in the Frequently Asked
    Question (FAQ) documents.

    Does Perl have a year 2000 problem?  Is Perl Y2K compliant?

    Short answer: No, Perl does not have a year 2000 problem.  Yes,
	   Perl is Y2K compliant (whatever that means).  The
	   programmers you've hired to use it, however, probably are
	   not.  If you want perl to complain when your programmers
	   create programs with certain types of possible year 2000
	   problems, a build option allows you to turn on warnings.

    Long answer: The question belies a true understanding of the
	   issue.  Perl is just as Y2K compliant as your pencil
	   --no more, and no less.  Can you use your pencil to write
	   a non-Y2K-compliant memo?  Of course you can.  Is that
	   the pencil's fault?  Of course it isn't.

	   The date and time functions supplied with perl (gmtime and
	   localtime) supply adequate information to determine the
	   year well beyond 2000 (2038 is when trouble strikes for
	   32-bit machines).  The year returned by these functions
	   when used in an array context is the year minus 1900.  For
	   years between 1910 and 1999 this happens to be a 2-digit
	   decimal number. To avoid the year 2000 problem simply do
	   not treat the year as a 2-digit number.  It isn't.

	   When gmtime() and localtime() are used in scalar context
	   they return a timestamp string that contains a fully-
	   expanded year.  For example, $timestamp =
	   gmtime(1005613200) sets $timestamp to "Tue Nov 13 01:00:00
	   2001".  There's no year 2000 problem here.

	   That doesn't mean that Perl can't be used to create non-
	   Y2K compliant programs.  It can.  But so can your pencil.
	   It's the fault of the user, not the language.  At the risk
	   of inflaming the NRA: ``Perl doesn't break Y2K, people
	   do.''  See http://language.perl.com/news/y2k.html for a
	   longer exposition.

	   If you want perl to warn you when it sees a program which
	   catenates a number with the string "19" -- a common
	   indication of a year 2000 problem -- build perl using the
	   Configure option  "-Accflags=-DPERL_Y2KWARN".
	   (See the file INSTALL for more information about building
	   perl.)