[Bug 1190421] [NEW] perl converts localtime into gmt before subtraction

Launchpad Bug Tracker 1190421 at bugs.launchpad.net
Thu Jun 13 13:08:30 UTC 2013 

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When I compare two timestamps in perl, I am getting wrong result, it's
shifted by a timezone.

The code:

use Time::Local;
use Time::Piece;

$time_now = localtime; # first time is specified by localtime
$time_future = Time::Piece->strptime("2013-08-13 01:30:00", "%Y-%m-%d %H:%M:%S"); # time in future is specified manually
print "Now it is $time_now\n"; # this is exactly the same time I have on my watch, my timezone, it's OK
print "We are going on holiday at $time_future\n"; # this is also OK, exactly the same time I have entered manually
# BUT....
$diff = $time_future - $time_now;
print "Remaining: $diff\n";
# HERE IS THE PROBLEM --- THE REMAINING TIME IS SHIFTED FROM WHAT I COUNT ON CALCULATOR BY MI TIMEZONE SHIFT

It looks like the localtime has information about my timezone and when
it has to be subtracted, it is shifted by the timezone and I subtract
GMT version, which is wrong!

Note: My country uses daylight saving time, but it's not the problem.
Both compared times are in dst and the error is bigger than 1 hour.

Google knows nothing about it.

=== ADDITIONAL INFO ===

Description:	Ubuntu 12.04.1 LTS
Release:	12.04

My version of perl: This is perl 5, version 14, subversion 2 (v5.14.2)
built for i686-linux-gnu-thread-multi-64int

saruman at William:~/prg/perl$ perl -V
Summary of my perl5 (revision 5 version 14 subversion 2) configuration:
   
  Platform:
    osname=linux, osvers=2.6.42-23-generic, archname=i686-linux-gnu-thread-multi-64int
    uname='linux panlong 2.6.42-23-generic #36-ubuntu smp tue apr 10 20:39:51 utc 2012 i686 i686 i386 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=i686-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.14 -Darchlib=/usr/lib/perl/5.14 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.14.2 -Dsitearch=/usr/local/lib/perl/5.14.2 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib -Dlibperl=libperl.so.5.14.2 -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.6.3', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /lib/i386-linux-gnu /lib/../lib /usr/lib/i386-linux-gnu /usr/lib/../lib /lib /usr/lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=, so=so, useshrplib=true, libperl=libperl.so.5.14.2
    gnulibc_version='2.15'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib -fstack-protector'


Characteristics of this binary (from libperl): 
  Compile-time options: MULTIPLICITY PERL_DONT_CREATE_GVSV
                        PERL_IMPLICIT_CONTEXT PERL_MALLOC_WRAP
                        PERL_PRESERVE_IVUV USE_64_BIT_INT USE_ITHREADS
                        USE_LARGE_FILES USE_PERLIO USE_PERL_ATOF
                        USE_REENTRANT_API
  Locally applied patches:
	DEBPKG:debian/arm_thread_stress_timeout - http://bugs.debian.org/501970 Raise the timeout of ext/threads/shared/t/stress.t to accommodate slower build hosts
	DEBPKG:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS default for modules installed from CPAN.
	DEBPKG:debian/db_file_ver - http://bugs.debian.org/340047 Remove overly restrictive DB_File version check.
	DEBPKG:debian/doc_info - Replace generic man(1) instructions with Debian-specific information.
	DEBPKG:debian/enc2xs_inc - http://bugs.debian.org/290336 Tweak enc2xs to follow symlinks and ignore missing @INC directories.
	DEBPKG:debian/errno_ver - http://bugs.debian.org/343351 Remove Errno version check due to upgrade problems with long-running processes.
	DEBPKG:debian/libperl_embed_doc - http://bugs.debian.org/186778 Note that libperl-dev package is required for embedded linking
	DEBPKG:fixes/respect_umask - Respect umask during installation
	DEBPKG:debian/writable_site_dirs - Set umask approproately for site install directories
	DEBPKG:debian/extutils_set_libperl_path - EU:MM: Set location of libperl.a to /usr/lib
	DEBPKG:debian/no_packlist_perllocal - Don't install .packlist or perllocal.pod for perl or vendor
	DEBPKG:debian/prefix_changes - Fiddle with *PREFIX and variables written to the makefile
	DEBPKG:debian/fakeroot - Postpone LD_LIBRARY_PATH evaluation to the binary targets.
	DEBPKG:debian/instmodsh_doc - Debian policy doesn't install .packlist files for core or vendor.
	DEBPKG:debian/ld_run_path - Remove standard libs from LD_RUN_PATH as per Debian policy.
	DEBPKG:debian/libnet_config_path - Set location of libnet.cfg to /etc/perl/Net as /usr may not be writable.
	DEBPKG:debian/m68k_thread_stress - http://bugs.debian.org/517938 http://bugs.debian.org/495826 Disable some threads tests on m68k for now due to missing TLS.
	DEBPKG:debian/mod_paths - Tweak @INC ordering for Debian
	DEBPKG:debian/module_build_man_extensions - http://bugs.debian.org/479460 Adjust Module::Build manual page extensions for the Debian Perl policy
	DEBPKG:debian/prune_libs - http://bugs.debian.org/128355 Prune the list of libraries wanted to what we actually need.
	DEBPKG:fixes/net_smtp_docs - [rt.cpan.org #36038] http://bugs.debian.org/100195 Document the Net::SMTP 'Port' option
	DEBPKG:debian/perlivp - http://bugs.debian.org/510895 Make perlivp skip include directories in /usr/local
	DEBPKG:debian/disable-zlib-bundling - Disable zlib bundling in Compress::Raw::Zlib
	DEBPKG:debian/cpanplus_definstalldirs - http://bugs.debian.org/533707 Configure CPANPLUS to use the site directories by default.
	DEBPKG:debian/cpanplus_config_path - Save local versions of CPANPLUS::Config::System into /etc/perl.
	DEBPKG:debian/deprecate-with-apt - http://bugs.debian.org/580034 Point users to Debian packages of deprecated core modules
	DEBPKG:fixes/hurd-ccflags - [a190e64] http://bugs.debian.org/587901 [perl #92244] Make hints/gnu.sh append to $ccflags rather than overriding them
	DEBPKG:debian/squelch-locale-warnings - http://bugs.debian.org/508764 Squelch locale warnings in Debian package maintainer scripts
	DEBPKG:debian/skip-upstream-git-tests - Skip tests specific to the upstream Git repository
	DEBPKG:fixes/extutils-cbuilder-cflags - [011e8fb] http://bugs.debian.org/624460 [perl #89478] Append CFLAGS and LDFLAGS to their Config.pm counterparts in EU::CBuilder
	DEBPKG:fixes/module-build-home-directory - http://bugs.debian.org/624850 [rt.cpan.org #67893] Fix failing tilde test when run under a UID without a passwd entry
	DEBPKG:debian/patchlevel - http://bugs.debian.org/567489 List packaged patches for 5.14.2-6ubuntu2.2 in patchlevel.h
	DEBPKG:fixes/h2ph-multiarch - [e7ec705] http://bugs.debian.org/625808 [perl #90122] Make h2ph correctly search gcc include directories
	DEBPKG:fixes/index-tainting - [3b36395] http://bugs.debian.org/291450 [perl #64804] RT 64804: tainting with index() of a constant
	DEBPKG:debian/skip-kfreebsd-crash - http://bugs.debian.org/628493 [perl #96272] Skip a crashing test case in t/op/threads.t on GNU/kFreeBSD
	DEBPKG:fixes/document_makemaker_ccflags - http://bugs.debian.org/628522 [rt.cpan.org #68613] Document that CCFLAGS should include $Config{ccflags}
	DEBPKG:fixes/sys-syslog-socket-timeout-kfreebsd.patch - http://bugs.debian.org/627821 [rt.cpan.org #69997] Use a socket timeout on GNU/kFreeBSD to catch ICMP port unreachable messages
	DEBPKG:fixes/hurd-hints - http://bugs.debian.org/636609 Improve general GNU hints, needed for GNU/Hurd.
	DEBPKG:fixes/pod_fixes - [7698aed] http://bugs.debian.org/637816 Fix typos in several pod/perl*.pod files
	DEBPKG:debian/find_html2text - http://bugs.debian.org/640479 Configure CPAN::Distribution with correct name of html2text
	DEBPKG:fixes/digest_eval_hole - http://bugs.debian.org/644108 Close the eval "require $module" security hole in Digest->new($algorithm)
	DEBPKG:fixes/hurd-ndbm - [f0d0a20] [perl #102680] http://bugs.debian.org/645989 Add GNU/Hurd hints for NDBM_File
	DEBPKG:fixes/sysconf.t-posix - [8040185] [perl #102888] http://bugs.debian.org/646016 Fix hang in ext/POSIX/t/sysconf.t on GNU/Hurd
	DEBPKG:fixes/hurd-largefile - [1fda587] [perl #103014] http://bugs.debian.org/645790 enable LFS on GNU/Hurd
	DEBPKG:debian/hurd_test_todo_syslog - http://bugs.debian.org/650093 Disable failing GNU/Hurd tests in cpan/Sys-Syslog/t/syslog.t
	DEBPKG:fixes/hurd_skip_itimer_virtual - [rt.cpan.org #72754] http://bugs.debian.org/650094 Skip interval timer tests in Time::HiRes on GNU/Hurd
	DEBPKG:debian/hurd_test_skip_socketpair - http://bugs.debian.org/650186 Disable failing GNU/Hurd tests ext/Socket/t/socketpair.t
	DEBPKG:debian/hurd_test_skip_sigdispatch - http://bugs.debian.org/650188 Disable failing GNU/Hurd tests op/sigdispatch.t
	DEBPKG:debian/hurd_test_skip_stack - http://bugs.debian.org/650175 Disable failing GNU/Hurd tests dist/threads/t/stack.t
	DEBPKG:debian/hurd_test_skip_recv - http://bugs.debian.org/650095 Disable failing GNU/Hurd tests cpan/autodie/t/recv.t
	DEBPKG:debian/hurd_test_skip_libc - http://bugs.debian.org/650097 Disable failing GNU/Hurd tests dist/threads/t/libc.t
	DEBPKG:debian/hurd_test_skip_pipe - http://bugs.debian.org/650187 Disable failing GNU/Hurd tests io/pipe.t
	DEBPKG:debian/hurd_test_skip_io_pipe - http://bugs.debian.org/650096 Disable failing GNU/Hurd tests dist/IO/t/io_pipe.t
	DEBPKG:fixes/CVE-2012-5195 - avoid calling memset with a negative count
	DEBPKG:fixes/CVE-2012-5526 - [PATCH 1/4] CR escaping for P3P header
  Built under linux
  Compiled at Nov 27 2012 00:14:48
  @INC:
    /etc/perl
    /usr/local/lib/perl/5.14.2
    /usr/local/share/perl/5.14.2
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.14
    /usr/share/perl/5.14
    /usr/local/lib/site_perl
    .

** Affects: perl (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: bot-comment
-- 
perl converts localtime into gmt before subtraction
https://bugs.launchpad.net/bugs/1190421
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