t/38local-subtract.t - metacpan.org

use strict;
use warnings;

use Test::More;

use DateTime;

# These tests should be the final word on dt subtraction involving a
# DST-changing time zone

{
    my $dt1 = DateTime->new(
        year      => 2003, month => 5, day => 6,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month => 11, day => 6,
        time_zone => 'America/Chicago',
    );

    my $dur1    = $dt2->subtract_datetime($dt1);
    my %deltas1 = $dur1->deltas;
    is( $deltas1{months},  6, 'delta_months is 6' );
    is( $deltas1{days},    0, 'delta_days is 0' );
    is( $deltas1{minutes}, 0, 'delta_minutes is 0' );
    is( $deltas1{seconds}, 0, 'delta_seconds is 0' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur1), $dt2 ), 0,
        'subtract_datetime is reversible from start point'
    );
    is(
        DateTime->compare( $dt2->clone->subtract_duration($dur1), $dt1 ), 0,
        'subtract_datetime is reversible from end point'
    );
    is( $deltas1{nanoseconds}, 0, 'delta_nanoseconds is 0' );

    my $dur2    = $dt1->subtract_datetime($dt2);
    my %deltas2 = $dur2->deltas;
    is( $deltas2{months},      -6, 'delta_months is -6' );
    is( $deltas2{days},        0,  'delta_days is 0' );
    is( $deltas2{minutes},     0,  'delta_minutes is 0' );
    is( $deltas2{seconds},     0,  'delta_seconds is 0' );
    is( $deltas2{nanoseconds}, 0,  'delta_nanoseconds is 0' );

    my $dur3    = $dt2->delta_md($dt1);
    my %deltas3 = $dur3->deltas;
    is( $deltas3{months},      6, 'delta_months is 6' );
    is( $deltas3{days},        0, 'delta_days is 0' );
    is( $deltas3{minutes},     0, 'delta_minutes is 0' );
    is( $deltas3{seconds},     0, 'delta_seconds is 0' );
    is( $deltas3{nanoseconds}, 0, 'delta_nanoseconds is 0' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur3), $dt2 ), 0,
        'delta_md is reversible from start point'
    );
    is(
        DateTime->compare( $dt2->clone->subtract_duration($dur3), $dt1 ), 0,
        'delta_md is reversible from end point'
    );

    my $dur4    = $dt2->delta_days($dt1);
    my %deltas4 = $dur4->deltas;
    is( $deltas4{months},      0,   'delta_months is 0' );
    is( $deltas4{days},        184, 'delta_days is 184' );
    is( $deltas4{minutes},     0,   'delta_minutes is 0' );
    is( $deltas4{seconds},     0,   'delta_seconds is 0' );
    is( $deltas4{nanoseconds}, 0,   'delta_nanoseconds is 0' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur3), $dt2 ), 0,
        'delta_days is reversible from start point'
    );
    is(
        DateTime->compare( $dt2->clone->subtract_duration($dur4), $dt1 ), 0,
        'delta_days is reversible from end point'
    );
}

# same as above, but now the UTC hour of the earlier datetime is
# _greater_ than that of the later one.  this checks that overflows
# are handled correctly.
{
    my $dt1 = DateTime->new(
        year      => 2003, month => 5, day => 6, hour => 18,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month => 11, day => 6, hour => 18,
        time_zone => 'America/Chicago',
    );

    my $dur1    = $dt2->subtract_datetime($dt1);
    my %deltas1 = $dur1->deltas;
    is( $deltas1{months},      6, 'delta_months is 6' );
    is( $deltas1{days},        0, 'delta_days is 0' );
    is( $deltas1{minutes},     0, 'delta_minutes is 0' );
    is( $deltas1{seconds},     0, 'delta_seconds is 0' );
    is( $deltas1{nanoseconds}, 0, 'delta_nanoseconds is 0' );
}

# make sure delta_md and delta_days work in the face of DST change
# where we lose an hour
{
    my $dt1 = DateTime->new(
        year      => 2003, month => 11, day => 6,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2004, month => 5, day => 6,
        time_zone => 'America/Chicago',
    );

    my $dur1    = $dt2->delta_md($dt1);
    my %deltas1 = $dur1->deltas;
    is( $deltas1{months},      6, 'delta_months is 6' );
    is( $deltas1{days},        0, 'delta_days is 0' );
    is( $deltas1{minutes},     0, 'delta_minutes is 0' );
    is( $deltas1{seconds},     0, 'delta_seconds is 0' );
    is( $deltas1{nanoseconds}, 0, 'delta_nanoseconds is 0' );

    my $dur2    = $dt2->delta_days($dt1);
    my %deltas2 = $dur2->deltas;
    is( $deltas2{months},      0,   'delta_months is 0' );
    is( $deltas2{days},        182, 'delta_days is 182' );
    is( $deltas2{minutes},     0,   'delta_minutes is 0' );
    is( $deltas2{seconds},     0,   'delta_seconds is 0' );
    is( $deltas2{nanoseconds}, 0,   'delta_nanoseconds is 0' );

}

# the docs say use UTC to guarantee reversibility
{
    my $dt1 = DateTime->new(
        year      => 2003, month => 5, day => 6,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month => 11, day => 6,
        time_zone => 'America/Chicago',
    );

    $dt1->set_time_zone('UTC');
    $dt2->set_time_zone('UTC');

    my $dur = $dt2->subtract_datetime($dt1);

    is(
        DateTime->compare( $dt1->add_duration($dur), $dt2 ), 0,
        'subtraction is reversible from start point with UTC'
    );
    is(
        DateTime->compare( $dt2->subtract_duration($dur), $dt2 ), 0,
        'subtraction is reversible from start point with UTC'
    );
}

# The important thing here is that after a subtraction, we can use the
# duration to get from one date to the other, regardless of the type
# of subtraction done.
{
    my $dt1 = DateTime->new(
        year      => 2003, month => 5, day => 6,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month => 11, day => 6,
        time_zone => 'America/Chicago',
    );

    my $dur1 = $dt2->subtract_datetime_absolute($dt1);

    my %deltas1 = $dur1->deltas;
    is( $deltas1{months},      0,        'delta_months is 0' );
    is( $deltas1{days},        0,        'delta_days is 0' );
    is( $deltas1{minutes},     0,        'delta_minutes is 0' );
    is( $deltas1{seconds},     15901200, 'delta_seconds is 15901200' );
    is( $deltas1{nanoseconds}, 0,        'delta_nanoseconds is 0' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur1), $dt2 ), 0,
        'subtraction is reversible'
    );
    is(
        DateTime->compare( $dt2->clone->subtract_duration($dur1), $dt1 ), 0,
        'subtraction is doubly reversible'
    );

    my $dur2 = $dt1->subtract_datetime_absolute($dt2);

    my %deltas2 = $dur2->deltas;
    is( $deltas2{months},      0,         'delta_months is 0' );
    is( $deltas2{days},        0,         'delta_days is 0' );
    is( $deltas2{minutes},     0,         'delta_minutes is 0' );
    is( $deltas2{seconds},     -15901200, 'delta_seconds is -15901200' );
    is( $deltas2{nanoseconds}, 0,         'delta_nanoseconds is 0' );

    is(
        DateTime->compare( $dt2->clone->add_duration($dur2), $dt1 ), 0,
        'subtraction is reversible'
    );
    is(
        DateTime->compare( $dt1->clone->subtract_duration($dur2), $dt2 ), 0,
        'subtraction is doubly reversible'
    );
}

{
    my $dt1 = DateTime->new(
        year      => 2003, month  => 4, day => 6,
        hour      => 1,    minute => 58,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month  => 4, day => 6,
        hour      => 3,    minute => 1,
        time_zone => 'America/Chicago',
    );

    my $dur = $dt2->subtract_datetime($dt1);

    my %deltas = $dur->deltas;
    is( $deltas{months},      0, 'delta_months is 0' );
    is( $deltas{days},        0, 'delta_days is 0' );
    is( $deltas{minutes},     3, 'delta_minutes is 3' );
    is( $deltas{seconds},     0, 'delta_seconds is 0' );
    is( $deltas{nanoseconds}, 0, 'delta_nanoseconds is 0' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur), $dt2 ), 0,
        'subtraction is reversible'
    );
    is(
        DateTime->compare( $dt2->clone->subtract_duration($dur), $dt1 ), 0,
        'subtraction is doubly reversible'
    );
}

{
    my $dt1 = DateTime->new(
        year      => 2003, month  => 4, day => 5,
        hour      => 1,    minute => 58,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month  => 4, day => 6,
        hour      => 3,    minute => 1,
        time_zone => 'America/Chicago',
    );

    my $dur = $dt2->subtract_datetime($dt1);

    my %deltas = $dur->deltas;
    is( $deltas{months},      0, 'delta_months is 0' );
    is( $deltas{days},        1, 'delta_days is 1' );
    is( $deltas{minutes},     3, 'delta_minutes is 3' );
    is( $deltas{seconds},     0, 'delta_seconds is 0' );
    is( $deltas{nanoseconds}, 0, 'delta_nanoseconds is 0' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur), $dt2 ), 0,
        'dt1 + dur = dt2'
    );

    # this are two examples from the docs
    is(
        DateTime->compare(
            $dt2->clone->subtract_duration($dur),
            $dt1->clone->add( hours => 1 )
        ),
        0,
        'dt2 - dur != dt1 (not reversible)'
    );
    is(
        DateTime->compare(
            $dt2->clone->subtract_duration( $dur->clock_duration )
                ->subtract_duration( $dur->calendar_duration ),
            $dt1
        ),
        0,
        'dt2 - dur->clock - dur->cal = dt1 (reversible when componentized)'
    );

    my $dur2    = $dt1->subtract_datetime($dt2);
    my %deltas2 = $dur2->deltas;
    is( $deltas2{months},      0,  'delta_months is 0' );
    is( $deltas2{days},        -1, 'delta_days is 1' );
    is( $deltas2{minutes},     -3, 'delta_minutes is 3' );
    is( $deltas2{seconds},     0,  'delta_seconds is 0' );
    is( $deltas2{nanoseconds}, 0,  'delta_nanoseconds is 0' );
    is( $dt2->clone->add_duration($dur2)->datetime, '2003-04-05T02:58:00',
        'dt2 + dur2 != dt1' );
    is(
        DateTime->compare(
            $dt2->clone->add_duration( $dur2->clock_duration )
                ->add_duration( $dur2->calendar_duration ),
            $dt1
        ),
        0,
        'dt2 + dur2->clock + dur2->cal = dt1'
    );
    is(
        DateTime->compare( $dt1->clone->subtract_duration($dur2), $dt2 ), 0,
        'dt1 - dur2 = dt2'
    );

}

# These tests makes sure that days with DST changes are "normal" when
# they're the smaller operand
{
    my $dt1 = DateTime->new(
        year      => 2003, month  => 4, day => 6,
        hour      => 3,    minute => 1,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month  => 4, day => 7,
        hour      => 3,    minute => 2,
        time_zone => 'America/Chicago',
    );

    my $dur = $dt2->subtract_datetime($dt1);

    my %deltas = $dur->deltas;
    is( $deltas{months},      0, 'delta_months is 0' );
    is( $deltas{days},        1, 'delta_days is 1' );
    is( $deltas{minutes},     1, 'delta_minutes is 1' );
    is( $deltas{seconds},     0, 'delta_seconds is 0' );
    is( $deltas{nanoseconds}, 0, 'delta_nanoseconds is 0' );

    my $dur2 = $dt1->subtract_datetime($dt2);

    my %deltas2 = $dur2->deltas;
    is( $deltas2{months},      0,  'delta_months is 0' );
    is( $deltas2{days},        -1, 'delta_days is -1' );
    is( $deltas2{minutes},     -1, 'delta_minutes is -1' );
    is( $deltas2{seconds},     0,  'delta_seconds is 0' );
    is( $deltas2{nanoseconds}, 0,  'delta_nanoseconds is 0' );

}

{
    my $dt1 = DateTime->new(
        year      => 2003, month  => 4, day => 5,
        hour      => 1,    minute => 58,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month  => 4, day => 7,
        hour      => 2,    minute => 1,
        time_zone => 'America/Chicago',
    );

    my $dur = $dt2->subtract_datetime($dt1);

    my %deltas = $dur->deltas;
    is( $deltas{months},      0, 'delta_months is 0' );
    is( $deltas{days},        2, 'delta_days is 2' );
    is( $deltas{minutes},     3, 'delta_minutes is 3' );
    is( $deltas{seconds},     0, 'delta_seconds is 0' );
    is( $deltas{nanoseconds}, 0, 'delta_nanoseconds is 0' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur), $dt2 ), 0,
        'subtraction is reversible'
    );
    is(
        DateTime->compare( $dt2->clone->subtract_duration($dur), $dt1 ), 0,
        'subtraction is doubly reversible'
    );
}

# from example in docs
{
    my $dt1 = DateTime->new(
        year      => 2003, month => 5, day => 6,
        time_zone => 'America/Chicago',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month => 11, day => 6,
        time_zone => 'America/Chicago',
    );

    $dt1->set_time_zone('floating');
    $dt2->set_time_zone('floating');

    my $dur    = $dt2->subtract_datetime($dt1);
    my %deltas = $dur->deltas;
    is( $deltas{months},      6, 'delta_months is 6' );
    is( $deltas{days},        0, 'delta_days is 0' );
    is( $deltas{minutes},     0, 'delta_minutes is 0' );
    is( $deltas{seconds},     0, 'delta_seconds is 0' );
    is( $deltas{nanoseconds}, 0, 'delta_nanoseconds is 0' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur), $dt2 ), 0,
        'subtraction is reversible from start point'
    );
    is(
        DateTime->compare( $dt2->clone->subtract_duration($dur), $dt1 ), 0,
        'subtraction is reversible from end point'
    );
}

{
    my $dt1 = DateTime->new(
        year      => 2005, month => 8,
        time_zone => 'Europe/London',
    );

    my $dt2 = DateTime->new(
        year      => 2005, month => 11,
        time_zone => 'Europe/London',
    );

    my $dur    = $dt2->subtract_datetime($dt1);
    my %deltas = $dur->deltas;
    is( $deltas{months}, 3,
        '3 months between two local times over DST change' );
    is( $deltas{days}, 0, '0 days between two local times over DST change' );
    is( $deltas{minutes}, 0,
        '0 minutes between two local times over DST change' );
}

# same as previous but without hours overflow
{
    my $dt1 = DateTime->new(
        year      => 2005, month => 8, hour => 12,
        time_zone => 'Europe/London',
    );

    my $dt2 = DateTime->new(
        year      => 2005, month => 11, hour => 12,
        time_zone => 'Europe/London',
    );

    my $dur    = $dt2->subtract_datetime($dt1);
    my %deltas = $dur->deltas;
    is( $deltas{months}, 3,
        '3 months between two local times over DST change' );
    is( $deltas{days}, 0, '0 days between two local times over DST change' );
    is( $deltas{minutes}, 0,
        '0 minutes between two local times over DST change' );
}

# another docs example
{
    my $dt2 = DateTime->new(
        year      => 2003, month => 10, day => 26,
        hour      => 1,
        time_zone => 'America/Chicago',
    );

    my $dt1 = $dt2->clone->subtract( hours => 1 );

    my $dur = $dt2->subtract_datetime($dt1);

    my %deltas = $dur->deltas;
    is( $deltas{months}, 0,
        '0 months between two local times over DST change' );
    is( $deltas{days}, 0, '0 days between two local times over DST change' );
    is( $deltas{minutes}, 60,
        '60 minutes between two local times over DST change' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur), $dt2 ), 0,
        'subtraction is reversible'
    );
    is(
        DateTime->compare( $dt2->clone->subtract_duration($dur), $dt1 ), 0,
        'subtraction is doubly reversible'
    );
}

{
    my $dt1 = DateTime->new(
        year      => 2003, month => 5, day => 6,
        time_zone => 'America/New_York',
    );

    my $dt2 = DateTime->new(
        year      => 2003, month => 5, day => 6,
        time_zone => 'America/Chicago',
    );

    my $dur = $dt2->subtract_datetime($dt1);

    my %deltas = $dur->deltas;
    is( $deltas{months}, 0,
        '0 months between two local times over DST change' );
    is( $deltas{days}, 0, '0 days between two local times over DST change' );
    is( $deltas{minutes}, 60,
        '60 minutes between two local times over DST change' );

    is(
        DateTime->compare( $dt1->clone->add_duration($dur), $dt2 ), 0,
        'subtraction is reversible'
    );
    is(
        DateTime->compare( $dt2->clone->subtract_duration($dur), $dt1 ), 0,
        'subtraction is doubly reversible'
    );
}

# Fix a bug that occurred when the local time zone had DST and the two
# datetime objects were on the same day
{
    my $dt1 = DateTime->new(
        year      => 2005, month  => 4, day => 3,
        hour      => 7,    minute => 0,
        time_zone => 'America/New_York'
    );

    my $dt2 = DateTime->new(
        year      => 2005, month  => 4, day => 3,
        hour      => 8,    minute => 0,
        time_zone => 'America/New_York'
    );

    my $dur = $dt2->subtract_datetime($dt1);
    my ( $minutes, $seconds ) = $dur->in_units( 'minutes', 'seconds' );

    is( $minutes, 60,
        'subtraction of two dates on a DST change date, minutes == 60' );
    is( $seconds, 0,
        'subtraction of two dates on a DST change date, seconds == 0' );

    $dur = $dt1->subtract_datetime($dt1);
    ok( $dur->is_zero,
        'dst change date (no dst) - itself, duration is zero' );
}

{
    my $dt1 = DateTime->new(
        year      => 2005, month  => 4, day => 3,
        hour      => 1,    minute => 0,
        time_zone => 'America/New_York'
    );

    my $dur = $dt1->subtract_datetime($dt1);
    ok( $dur->is_zero,
        'dst change date (with dst) - itself, duration is zero' );
}

# This tests a bug where one of the datetimes is changing DST, and the
# other is not. In this case, no "adjustments" (aka hacks) are made in
# subtract_datetime, and it just gives the "UTC difference".
{

    # This is UTC-4
    my $dt1 = DateTime->new(
        year      => 2009, month => 3, day => 9,
        time_zone => 'America/New_York'
    );

    # This is UTC+8
    my $dt2 = DateTime->new(
        year      => 2009, month => 3, day => 9,
        time_zone => 'Asia/Hong_Kong'
    );

    my $dur = $dt1->subtract_datetime($dt2);

    is(
        $dur->delta_minutes, 720,
        'subtraction the day after a DST change in one zone, where the other datetime is in a different zone'
    );
}

{

    # This is UTC-5
    my $dt1 = DateTime->new(
        year      => 2009, month => 3, day => 8,
        hour      => 1,
        time_zone => 'America/New_York'
    );

    # This is UTC+8
    my $dt2 = DateTime->new(
        year      => 2009, month => 3, day => 8,
        hour      => 1,
        time_zone => 'Asia/Hong_Kong'
    );

    my $dur = $dt1->subtract_datetime($dt2);

    is(
        $dur->delta_minutes, 780,
        'subtraction the day of a DST change in one zone (before the change),'
            . ' where the other datetime is in a different zone'
    );
}

{

    # This is UTC-4
    my $dt1 = DateTime->new(
        year      => 2009, month => 3, day => 8,
        hour      => 4,
        time_zone => 'America/New_York'
    );

    # This is UTC+8
    my $dt2 = DateTime->new(
        year      => 2009, month => 3, day => 8,
        hour      => 4,
        time_zone => 'Asia/Hong_Kong'
    );

    my $dur = $dt1->subtract_datetime($dt2);

    is(
        $dur->delta_minutes, 720,
        'subtraction the day of a DST change in one zone (after the change),'
            . ' where the other datetime is in a different zone'
    );
}

done_testing();
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