From @steve-m-hay

This is a bug report for perl from Steve.Hay@uk.radan.com,
generated with the help of perlbug 1.34 running under perl v5.8.0.

When running on Windows NT/2000/XP Perl's built-in stat() function can
return the wrong last modification time of a file.

The value returned should be expressed as seconds since the Epoch, and
should therefore be independent of the system's time zone and daylight
savings time (DST) settings.

However, for a file created during a period when DST is in effect the
value actually returned when the system is no longer in a DST period
depends on whether or not the system is configured to automatically
make adjustments for DST.

Example:

Running on Windows XP Professional, Service Pack 1
"Regional and Language Options" set to English (United Kingdom)

Open the "Date and Time Properties" applet from Control Panel

Go to the "Time Zone" tab

Select "(GMT) Greenwich Mean Time: Dublin, Edinburgh, Lisbon, London"
and select the option to "Automatically adjust clock for daylight
saving changes"

Go to the "Date & Time" tab

Enter the values "1 June 2002" and "14:00:00" (when DST is in effect)

Click "OK" to save these settings and dismiss the applet

Open a Comment Prompt and type the following commands:

cd \Temp
echo Hello > test.txt

Now bring the "Date and Time Properties" applet back up, change the
values to "1 November 2002" and "14:00:00" (when DST is no longer in
effect) and click "OK" to save it

Type the following command in the Command Prompt:

perl -e "print +(stat 'test.txt')[9]"

This outputs a number like:

1022932805

depending on how soon you created the file 'test.txt' with the "echo"
command above after having set the time

Finally, bring the "Date and Time Properties" applet back up,
deselect the option to "Automatically adjust clock for daylight saving
changes" and click "OK" to save it

Repeat the above "perl" command in the Command Prompt, and a different
number is output, in this case:

1022936405

The two values are different by 3600 seconds, i.e. the amount that a DST
adjustment was made for. The last modification time of the file thus
cannot be determined since there is no way (?) to programmatically
determine whether or not the "Automatically adjust ..." setting is
selected or not.

I believe that this output is wrong. The value returned by stat() should
be the same regardless of whether the "Automatically adjust ..." setting
is selected or not.

One final note: stat() behaves as I would expect, i.e. always returning
the same value, on Windows 95/98/ME. It is only the "NT" type systems
(NT4/2000/XP) that have the problem.

Flags:
category=core
severity=medium

Site configuration information for perl v5.8.0:

Configured by radan at Thu Sep 5 09:10:23 2002.

Summary of my perl5 (revision 5 version 8 subversion 0) configuration:
Platform:
osname=MSWin32, osvers=4.0, archname=MSWin32-x86-perlio
uname=''
config_args='undef'
hint=recommended, useposix=true, d_sigaction=undef
usethreads=undef use5005threads=undef useithreads=undef
usemultiplicity=undef
useperlio=define d_sfio=undef uselargefiles=undef usesocks=undef
use64bitint=undef use64bitall=undef uselongdouble=undef
usemymalloc=y, bincompat5005=undef
Compiler:
cc='cl', ccflags ='-nologo -Gf -W3 -MD -DNDEBUG -O1 -DWIN32
-D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT -DUSE_PERLIO
-DPERL_MSVCRT_READFIX',
optimize='-MD -DNDEBUG -O1',
cppflags='-DWIN32'
ccversion='', gccversion='', gccosandvers=''
intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=10
ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=4
alignbytes=8, prototype=define
Linker and Libraries:
ld='link', ldflags ='-nologo -nodefaultlib -release
-libpath:"C:\perl5\lib\CORE" -machine:x86'
libpth=D:\PROGRA~~1\MICROS~~1\VC98\lib "D:\openssl\lib"
libs=libeay32.lib oldnames.lib kernel32.lib user32.lib gdi32.lib
winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib
oleaut32.lib netapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib
version.lib odbc32.lib odbccp32.lib msvcrt.lib
perllibs=libeay32.lib oldnames.lib kernel32.lib user32.lib
gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib
oleaut32.lib netapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib
version.lib odbc32.lib odbccp32.lib msvcrt.lib
libc=msvcrt.lib, so=dll, useshrplib=yes, libperl=perl58.lib
gnulibc_version='undef'
Dynamic Linking:
dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -release
-libpath:"C:\perl5\lib\CORE" -machine:x86'

Locally applied patches:

@INC for perl v5.8.0:
C:/perl5/lib
C:/perl5/site/lib
.

Environment for perl v5.8.0:
HOME (unset)
LANG (unset)
LANGUAGE (unset)
LD_LIBRARY_PATH (unset)
LOGDIR (unset)

PATH=C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\perl5\bin
PERL5LIB (unset)
PERL_BADLANG (unset)
SHELL (unset)

Last mod time from stat() can be wrong on Windows NT/2000/XP #6080

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