diff --git a/t/db_dependent/Calendar.t b/t/db_dependent/Calendar.t
index d6752b9da4..f938b5c79a 100755
--- a/t/db_dependent/Calendar.t
+++ b/t/db_dependent/Calendar.t
@@ -18,7 +18,7 @@
 use Modern::Perl;
 
 use Test::NoWarnings;
-use Test::More tests => 7;
+use Test::More tests => 8;
 use Time::Fake;
 
 use t::lib::Mocks;
@@ -26,6 +26,7 @@ use t::lib::TestBuilder;
 
 use DateTime;
 use DateTime::Duration;
+use C4::Calendar;
 use Koha::Caches;
 use Koha::Library::Calendar;
 use Koha::Database;
@@ -793,4 +794,59 @@ subtest 'get_push_amt' => sub {
     };
 };
 
+subtest 'insert_single_holiday/insert_exception_holiday update the in-memory cache' => sub {
+
+    # Migrated from t/db_dependent/Holidays.t (C4::Calendar in-memory cache sync)
+    plan tests => 4;
+
+    $schema->storage->txn_begin;
+
+    my $branchcode = $builder->build( { source => 'Branch' } )->{branchcode};
+    my $calendar   = C4::Calendar->new( branchcode => $branchcode );
+
+    my $single_day = dt_from_string()->add( days => 10 );
+    $calendar->insert_single_holiday(
+        day         => $single_day->day,
+        month       => $single_day->month,
+        year        => $single_day->year,
+        title       => 'Single',
+        description => '',
+    );
+    is(
+        $calendar->isHoliday( $single_day->day, $single_day->month, $single_day->year ), 1,
+        'isHoliday sees a single holiday just inserted on the same C4::Calendar object'
+    );
+
+    # Close every weekday so exception_day is a holiday until the exception is added.
+    foreach my $weekday ( 0 .. 6 ) {
+        $calendar->insert_week_day_holiday( weekday => $weekday, title => '', description => '' );
+    }
+
+    # insert_exception_holiday called with 'date' rather than day/month/year,
+    # exercising the date-string derivation path.
+    my $exception_day = dt_from_string()->add( days => 20 );
+    $calendar->insert_exception_holiday(
+        date        => $exception_day->ymd,
+        title       => 'Exception',
+        description => '',
+    );
+    is(
+        $calendar->isHoliday( $exception_day->day, $exception_day->month, $exception_day->year ), 0,
+        'isHoliday sees an exception holiday just inserted on the same C4::Calendar object, overriding the weekday closure'
+    );
+
+    # A second, freshly instantiated C4::Calendar object should agree.
+    my $reloaded = C4::Calendar->new( branchcode => $branchcode );
+    is(
+        $reloaded->isHoliday( $single_day->day, $single_day->month, $single_day->year ), 1,
+        'A freshly instantiated C4::Calendar also sees the single holiday'
+    );
+    is(
+        $reloaded->isHoliday( $exception_day->day, $exception_day->month, $exception_day->year ), 0,
+        'A freshly instantiated C4::Calendar also sees the exception holiday'
+    );
+
+    $schema->storage->txn_rollback;
+};
+
 $schema->storage->txn_rollback();
diff --git a/t/db_dependent/Holidays.t b/t/db_dependent/Holidays.t
deleted file mode 100755
index 4572a668dc..0000000000
--- a/t/db_dependent/Holidays.t
+++ /dev/null
@@ -1,443 +0,0 @@
-#!/usr/bin/perl
-
-# This file is part of Koha.
-#
-# Koha is free software; you can redistribute it and/or modify it
-# under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 3 of the License, or
-# (at your option) any later version.
-#
-# Koha is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with Koha; if not, see <https://www.gnu.org/licenses>.
-
-use Modern::Perl;
-
-use Test::NoWarnings;
-use Test::More tests => 16;
-use Test::Exception;
-
-use DateTime;
-use DateTime::TimeZone;
-
-use t::lib::TestBuilder;
-use C4::Context;
-use Koha::Database;
-use Koha::DateUtils qw( dt_from_string );
-
-BEGIN {
-    use_ok('Koha::Library::Calendar');
-    use_ok('C4::Calendar');
-}
-
-my $schema  = Koha::Database->new->schema;
-my $dbh     = C4::Context->dbh;
-my $builder = t::lib::TestBuilder->new;
-
-subtest 'is_holiday timezone tests' => sub {
-
-    plan tests => 1;
-
-    $schema->storage->txn_begin;
-
-    $dbh->do("DELETE FROM library_single_closures");
-    $dbh->do("DELETE FROM library_closure_exceptions");
-
-    # Clear cache
-    Koha::Caches->get_instance->flush_all;
-
-    # Artificially set timezone
-    my $timezone = 'America/Santiago';
-    $ENV{TZ} = $timezone;
-    use POSIX qw(tzset);
-    tzset;
-
-    my $branch   = $builder->build( { source => 'Branch' } )->{branchcode};
-    my $calendar = Koha::Library::Calendar->new( branchcode => $branch );
-
-    C4::Calendar->new( branchcode => $branch )->insert_exception_holiday(
-        day         => 6,
-        month       => 9,
-        year        => 2015,
-        title       => 'Invalid date',
-        description => 'Invalid date description',
-    );
-
-    my $exception_holiday = DateTime->new( day => 6, month => 9, year => 2015 );
-    my $now_dt            = DateTime->now;
-
-    my $diff;
-    eval { $diff = $calendar->days_between( $now_dt, $exception_holiday ) };
-    unlike(
-        $@,
-        qr/Invalid local time for date in time zone: America\/Santiago/,
-        'Avoid invalid datetime due to DST'
-    );
-
-    $schema->storage->txn_rollback;
-};
-
-$schema->storage->txn_begin;
-
-# Create two fresh branches for the tests
-my $branch_1 = $builder->build( { source => 'Branch' } )->{branchcode};
-my $branch_2 = $builder->build( { source => 'Branch' } )->{branchcode};
-
-C4::Calendar->new( branchcode => $branch_1 )->insert_week_day_holiday(
-    weekday     => 0,
-    title       => '',
-    description => 'Sundays',
-);
-
-my $holiday2add = dt_from_string("2015-01-01");
-C4::Calendar->new( branchcode => $branch_1 )->insert_day_month_holiday(
-    day         => $holiday2add->day(),
-    month       => $holiday2add->month(),
-    year        => $holiday2add->year(),
-    title       => '',
-    description => "New Year's Day",
-);
-$holiday2add = dt_from_string("2014-12-25");
-C4::Calendar->new( branchcode => $branch_1 )->insert_day_month_holiday(
-    day         => $holiday2add->day(),
-    month       => $holiday2add->month(),
-    year        => $holiday2add->year(),
-    title       => '',
-    description => 'Christmas',
-);
-
-my $koha_calendar = Koha::Library::Calendar->new( branchcode => $branch_1 );
-my $c4_calendar   = C4::Calendar->new( branchcode => $branch_1 );
-
-isa_ok( $koha_calendar, 'Koha::Library::Calendar', 'Koha::Library::Calendar class returned' );
-isa_ok( $c4_calendar,   'C4::Calendar',            'C4::Calendar class returned' );
-
-my $sunday = DateTime->new(
-    year  => 2011,
-    month => 6,
-    day   => 26,
-);
-my $monday = DateTime->new(
-    year  => 2011,
-    month => 6,
-    day   => 27,
-);
-my $christmas = DateTime->new(
-    year  => 2032,
-    month => 12,
-    day   => 25,
-);
-my $newyear = DateTime->new(
-    year  => 2035,
-    month => 1,
-    day   => 1,
-);
-
-is( $koha_calendar->is_holiday($sunday),    1, 'Sunday is a closed day' );
-is( $koha_calendar->is_holiday($monday),    0, 'Monday is not a closed day' );
-is( $koha_calendar->is_holiday($christmas), 1, 'Christmas is a closed day' );
-is( $koha_calendar->is_holiday($newyear),   1, 'New Years day is a closed day' );
-
-$dbh->do("DELETE FROM library_weekly_closures");
-$dbh->do("DELETE FROM library_repeating_closures");
-$dbh->do("DELETE FROM library_single_closures");
-$dbh->do("DELETE FROM library_closure_exceptions");
-
-my $custom_holiday = DateTime->new(
-    year  => 2013,
-    month => 11,
-    day   => 12,
-);
-
-my $today = dt_from_string();
-C4::Calendar->new( branchcode => $branch_2 )->insert_single_holiday(
-    day         => $today->day(),
-    month       => $today->month(),
-    year        => $today->year(),
-    title       => "$today",
-    description => "$today",
-);
-
-is(
-    Koha::Library::Calendar->new( branchcode => $branch_2 )->is_holiday($today), 1,
-    "Today is a holiday for $branch_2"
-);
-is(
-    Koha::Library::Calendar->new( branchcode => $branch_1 )->is_holiday($today), 0,
-    "Today is not a holiday for $branch_1"
-);
-
-$schema->storage->txn_rollback;
-
-subtest 'copy_to_branch' => sub {
-
-    plan tests => 10;
-
-    $schema->storage->txn_begin;
-
-    my $branch1   = $builder->build( { source => 'Branch' } )->{branchcode};
-    my $calendar1 = C4::Calendar->new( branchcode => $branch1 );
-    my $sunday    = dt_from_string("2020-03-15");
-    $calendar1->insert_week_day_holiday(
-        weekday     => 0,
-        title       => '',
-        description => 'Sundays',
-    );
-
-    my $day_month = dt_from_string("2020-03-17");
-    $calendar1->insert_day_month_holiday(
-        day         => $day_month->day(),
-        month       => $day_month->month(),
-        year        => $day_month->year(),
-        title       => '',
-        description => "",
-    );
-
-    my $future_date = dt_from_string("9999-12-31");
-    $calendar1->insert_single_holiday(
-        day         => $future_date->day(),
-        month       => $future_date->month(),
-        year        => $future_date->year(),
-        title       => "",
-        description => "",
-    );
-
-    my $future_exception = dt_from_string("9999-12-30");
-    $calendar1->insert_exception_holiday(
-        day         => $future_exception->day(),
-        month       => $future_exception->month(),
-        year        => $future_exception->year(),
-        title       => "",
-        description => "",
-    );
-
-    my $past_date = dt_from_string("2019-11-20");
-    $calendar1->insert_single_holiday(
-        day         => $past_date->day(),
-        month       => $past_date->month(),
-        year        => $past_date->year(),
-        title       => "",
-        description => "",
-    );
-
-    my $past_exception = dt_from_string("2020-03-09");
-    $calendar1->insert_exception_holiday(
-        day         => $past_exception->day(),
-        month       => $past_exception->month(),
-        year        => $past_exception->year(),
-        title       => "",
-        description => "",
-    );
-
-    my $branch2 = $builder->build( { source => 'Branch' } )->{branchcode};
-
-    C4::Calendar->new( branchcode => $branch1 )->copy_to_branch($branch2);
-
-    my $calendar2  = C4::Calendar->new( branchcode => $branch2 );
-    my $exceptions = $calendar2->get_exception_holidays;
-
-    is( $calendar2->isHoliday( $sunday->day, $sunday->month, $sunday->year ), 1, "Weekday holiday copied to branch 2" );
-    is(
-        $calendar2->isHoliday( $day_month->day, $day_month->month, $day_month->year ), 1,
-        "Day/month holiday copied to branch 2"
-    );
-    is(
-        $calendar2->isHoliday( $future_date->day, $future_date->month, $future_date->year ), 1,
-        "Single holiday copied to branch 2"
-    );
-    is( ( grep { $_->{date} eq "9999-12-30" } values %$exceptions ), 1, "Exception holiday copied to branch 2" );
-    is(
-        $calendar2->isHoliday( $past_date->day, $past_date->month, $past_date->year ), 0,
-        "Don't copy past single holidays"
-    );
-    is( ( grep { $_->{date} eq "2020-03-09" } values %$exceptions ), 0, "Don't copy past exception holidays " );
-
-    C4::Calendar->new( branchcode => $branch1 )->copy_to_branch($branch2);
-
-    #Select all rows with same values from database
-    my $dbh                 = C4::Context->dbh;
-    my $get_weekly_closures = "SELECT a.* FROM library_weekly_closures a
-        JOIN (SELECT library_id, weekday, COUNT(*)
-        FROM library_weekly_closures
-        GROUP BY library_id, weekday HAVING count(*) > 1) b
-        ON a.library_id = b.library_id AND a.weekday = b.weekday
-        ORDER BY a.library_id;";
-    my $sth = $dbh->prepare($get_weekly_closures);
-    $sth->execute;
-
-    my @weekly_closures;
-    while ( my $row = $sth->fetchrow_hashref ) {
-        push @weekly_closures, $row;
-    }
-
-    is( scalar(@weekly_closures), 0, "None of the weekly closures were doubled" );
-
-    my $get_repeating_closures = "SELECT a.* FROM library_repeating_closures a
-        JOIN (SELECT library_id, day, month, COUNT(*)
-        FROM library_repeating_closures
-        GROUP BY library_id, day, month HAVING count(*) > 1) b
-        ON a.library_id = b.library_id AND a.day = b.day AND a.month = b.month
-        ORDER BY a.library_id;";
-    $sth = $dbh->prepare($get_repeating_closures);
-    $sth->execute;
-
-    my @repeating_closures;
-    while ( my $row = $sth->fetchrow_hashref ) {
-        push @repeating_closures, $row;
-    }
-
-    is( scalar(@repeating_closures), 0, "None of the repeating closures were doubled" );
-
-    my $get_single_closures = "SELECT a.* FROM library_single_closures a
-        JOIN (SELECT library_id, date, COUNT(*)
-        FROM library_single_closures
-        GROUP BY library_id, date HAVING count(*) > 1) b
-        ON a.library_id = b.library_id AND a.date = b.date
-        ORDER BY a.library_id;";
-    $sth = $dbh->prepare($get_single_closures);
-    $sth->execute;
-
-    my @single_closures;
-    while ( my $row = $sth->fetchrow_hashref ) {
-        push @single_closures, $row;
-    }
-
-    is( scalar(@single_closures), 0, "None of the single closures were doubled" );
-
-    my $get_closure_exceptions = "SELECT a.* FROM library_closure_exceptions a
-        JOIN (SELECT library_id, date, COUNT(*)
-        FROM library_closure_exceptions
-        GROUP BY library_id, date HAVING count(*) > 1) b
-        ON a.library_id = b.library_id AND a.date = b.date
-        ORDER BY a.library_id;";
-    $sth = $dbh->prepare($get_closure_exceptions);
-    $sth->execute;
-
-    my @closure_exceptions;
-    while ( my $row = $sth->fetchrow_hashref ) {
-        push @closure_exceptions, $row;
-    }
-
-    is( scalar(@closure_exceptions), 0, "None of the closure exceptions were doubled" );
-
-    $schema->storage->txn_rollback;
-
-};
-
-subtest 'with a library that is never open' => sub {
-    plan tests => 2;
-
-    $schema->storage->txn_begin;
-
-    my $branchcode = $builder->build( { source => 'Branch' } )->{branchcode};
-    my $calendar   = C4::Calendar->new( branchcode => $branchcode );
-    foreach my $weekday ( 0 .. 6 ) {
-        $calendar->insert_week_day_holiday( weekday => $weekday, title => '', description => '' );
-    }
-
-    my $now = dt_from_string;
-
-    subtest 'next_open_days should throw an exception' => sub {
-        my $kcalendar = Koha::Library::Calendar->new( branchcode => $branchcode, days_mode => 'Calendar' );
-        throws_ok { $kcalendar->next_open_days( $now, 1 ) } 'Koha::Exceptions::Calendar::NoOpenDays';
-    };
-
-    subtest 'prev_open_days should throw an exception' => sub {
-        my $kcalendar = Koha::Library::Calendar->new( branchcode => $branchcode, days_mode => 'Calendar' );
-        throws_ok { $kcalendar->prev_open_days( $now, 1 ) } 'Koha::Exceptions::Calendar::NoOpenDays';
-    };
-
-    $schema->storage->txn_rollback;
-};
-
-subtest 'with a library that is *almost* never open' => sub {
-    plan tests => 2;
-
-    $schema->storage->txn_begin;
-
-    my $branchcode = $builder->build( { source => 'Branch' } )->{branchcode};
-    my $calendar   = C4::Calendar->new( branchcode => $branchcode );
-    foreach my $weekday ( 0 .. 6 ) {
-        $calendar->insert_week_day_holiday( weekday => $weekday, title => '', description => '' );
-    }
-
-    my $now                    = dt_from_string;
-    my $open_day_in_the_future = $now->clone()->add( years => 1 );
-    my $open_day_in_the_past   = $now->clone()->subtract( years => 1 );
-    $calendar->insert_exception_holiday( date => $open_day_in_the_future->ymd, title => '', description => '' );
-    $calendar->insert_exception_holiday( date => $open_day_in_the_past->ymd,   title => '', description => '' );
-
-    subtest 'next_open_days should find the open day' => sub {
-        my $kcalendar     = Koha::Library::Calendar->new( branchcode => $branchcode, days_mode => 'Calendar' );
-        my $next_open_day = $kcalendar->next_open_days( $now, 1 );
-        is( $next_open_day->ymd, $open_day_in_the_future->ymd );
-    };
-
-    subtest 'prev_open_days should find the open day' => sub {
-        my $kcalendar     = Koha::Library::Calendar->new( branchcode => $branchcode, days_mode => 'Calendar' );
-        my $prev_open_day = $kcalendar->prev_open_days( $now, 1 );
-        is( $prev_open_day->ymd, $open_day_in_the_past->ymd );
-    };
-
-    $schema->storage->txn_rollback;
-};
-
-subtest 'insert_single_holiday/insert_exception_holiday update the in-memory cache' => sub {
-    plan tests => 4;
-
-    $schema->storage->txn_begin;
-
-    my $branchcode = $builder->build( { source => 'Branch' } )->{branchcode};
-    my $calendar   = C4::Calendar->new( branchcode => $branchcode );
-
-    my $single_day = dt_from_string()->add( days => 10 );
-    $calendar->insert_single_holiday(
-        day         => $single_day->day,
-        month       => $single_day->month,
-        year        => $single_day->year,
-        title       => 'Single',
-        description => '',
-    );
-    is(
-        $calendar->isHoliday( $single_day->day, $single_day->month, $single_day->year ), 1,
-        'isHoliday sees a single holiday just inserted on the same C4::Calendar object'
-    );
-
-    # Close every weekday so exception_day is a holiday until the exception is added.
-    foreach my $weekday ( 0 .. 6 ) {
-        $calendar->insert_week_day_holiday( weekday => $weekday, title => '', description => '' );
-    }
-
-    # insert_exception_holiday called with 'date' rather than day/month/year,
-    # exercising the date-string derivation path.
-    my $exception_day = dt_from_string()->add( days => 20 );
-    $calendar->insert_exception_holiday(
-        date        => $exception_day->ymd,
-        title       => 'Exception',
-        description => '',
-    );
-    is(
-        $calendar->isHoliday( $exception_day->day, $exception_day->month, $exception_day->year ), 0,
-        'isHoliday sees an exception holiday just inserted on the same C4::Calendar object, overriding the weekday closure'
-    );
-
-    # A second, freshly instantiated C4::Calendar object should agree.
-    my $reloaded = C4::Calendar->new( branchcode => $branchcode );
-    is(
-        $reloaded->isHoliday( $single_day->day, $single_day->month, $single_day->year ), 1,
-        'A freshly instantiated C4::Calendar also sees the single holiday'
-    );
-    is(
-        $reloaded->isHoliday( $exception_day->day, $exception_day->month, $exception_day->year ), 0,
-        'A freshly instantiated C4::Calendar also sees the exception holiday'
-    );
-
-    $schema->storage->txn_rollback;
-};
-
-# Clear cache
-Koha::Caches->get_instance->flush_all;
diff --git a/t/db_dependent/Koha/Library/Calendar.t b/t/db_dependent/Koha/Library/Calendar.t
index c92b9bba76..1b5ec2a270 100755
--- a/t/db_dependent/Koha/Library/Calendar.t
+++ b/t/db_dependent/Koha/Library/Calendar.t
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 # Copyright 2025 Koha Development team
 #
@@ -19,13 +19,15 @@
 
 use Modern::Perl;
 
-use Test::More tests => 12;
+use Test::More tests => 15;
 use Test::Exception;
 use Test::NoWarnings;
 
 use Koha::Caches;
 use Koha::Database;
 use Koha::DateUtils qw( dt_from_string );
+
+use DateTime;
 use Koha::Library::Calendar::WeeklyClosures;
 use Koha::Library::Calendar::RepeatingClosures;
 use Koha::Library::Calendar::SingleClosures;
@@ -473,3 +475,167 @@ subtest 'delete_weekly_closure/delete_repeating_closure refresh in-process state
 
     $schema->storage->txn_rollback;
 };
+
+subtest 'is_holiday DST edge case' => sub {
+
+    # Migrated from t/db_dependent/Holidays.t
+    plan tests => 1;
+
+    $schema->storage->txn_begin;
+
+    Koha::Caches->get_instance->flush_all;
+
+    # Artificially set a timezone with a DST transition that historically
+    # triggered "Invalid local time for date in time zone" in date math.
+    local $ENV{TZ} = 'America/Santiago';
+    require POSIX;
+    POSIX::tzset();
+
+    my $library  = $builder->build_object( { class => 'Koha::Libraries' } );
+    my $calendar = Koha::Library::Calendar->new( branchcode => $library->branchcode );
+
+    $calendar->add_exception(
+        { date => '2015-09-06', title => 'Invalid date', description => 'Invalid date description' } );
+
+    my $exception_holiday = DateTime->new( day => 6, month => 9, year => 2015 );
+    my $now_dt            = dt_from_string;
+
+    my $diff;
+    eval { $diff = $calendar->days_between( $now_dt, $exception_holiday ) };
+    unlike(
+        $@,
+        qr{Invalid local time for date in time zone: America/Santiago},
+        'Avoid invalid datetime due to DST'
+    );
+
+    # Restore the process timezone so later teardown / end-of-run checks
+    # (e.g. Test::NoWarnings) are not affected by the artificial TZ.
+    delete $ENV{TZ};
+    POSIX::tzset();
+
+    $schema->storage->txn_rollback;
+};
+
+subtest 'next_open_days / prev_open_days' => sub {
+
+    # Migrated from t/db_dependent/Holidays.t
+    plan tests => 2;
+
+    subtest 'with a library that is never open' => sub {
+        plan tests => 2;
+
+        $schema->storage->txn_begin;
+
+        my $library    = $builder->build_object( { class => 'Koha::Libraries' } );
+        my $branchcode = $library->branchcode;
+        my $calendar   = Koha::Library::Calendar->new( branchcode => $branchcode );
+        $calendar->add_weekly_closure( { weekday => $_, title => '', description => '' } ) for ( 0 .. 6 );
+
+        my $now       = dt_from_string;
+        my $kcalendar = Koha::Library::Calendar->new( branchcode => $branchcode, days_mode => 'Calendar' );
+
+        throws_ok { $kcalendar->next_open_days( $now, 1 ) } 'Koha::Exceptions::Calendar::NoOpenDays',
+            'next_open_days throws when the library is never open';
+        throws_ok { $kcalendar->prev_open_days( $now, 1 ) } 'Koha::Exceptions::Calendar::NoOpenDays',
+            'prev_open_days throws when the library is never open';
+
+        $schema->storage->txn_rollback;
+    };
+
+    subtest 'with a library that is *almost* never open' => sub {
+        plan tests => 2;
+
+        $schema->storage->txn_begin;
+
+        my $library    = $builder->build_object( { class => 'Koha::Libraries' } );
+        my $branchcode = $library->branchcode;
+        my $calendar   = Koha::Library::Calendar->new( branchcode => $branchcode );
+        $calendar->add_weekly_closure( { weekday => $_, title => '', description => '' } ) for ( 0 .. 6 );
+
+        my $now                    = dt_from_string;
+        my $open_day_in_the_future = $now->clone->add( years => 1 );
+        my $open_day_in_the_past   = $now->clone->subtract( years => 1 );
+
+        # Exceptions override the weekly closures, making those single days open
+        $calendar->add_exception( { date => $open_day_in_the_future->ymd, title => '', description => '' } );
+        $calendar->add_exception( { date => $open_day_in_the_past->ymd,   title => '', description => '' } );
+
+        my $kcalendar = Koha::Library::Calendar->new( branchcode => $branchcode, days_mode => 'Calendar' );
+
+        is(
+            $kcalendar->next_open_days( $now, 1 )->ymd, $open_day_in_the_future->ymd,
+            'next_open_days finds the future open day created via an exception'
+        );
+        is(
+            $kcalendar->prev_open_days( $now, 1 )->ymd, $open_day_in_the_past->ymd,
+            'prev_open_days finds the past open day created via an exception'
+        );
+
+        $schema->storage->txn_rollback;
+    };
+};
+
+subtest 'copy_to completeness' => sub {
+
+    # Migrated from t/db_dependent/Holidays.t copy_to_branch: all four closure
+    # types copy, past-dated single/exception are excluded, and a second copy
+    # does not duplicate any of the four types.
+    plan tests => 8;
+
+    $schema->storage->txn_begin;
+
+    my $library  = $builder->build_object( { class => 'Koha::Libraries' } );
+    my $calendar = Koha::Library::Calendar->new( branchcode => $library->branchcode );
+
+    my $today = dt_from_string;
+    $calendar->add_weekly_closure( { weekday => 6, title => 'Saturdays', description => '' } );
+    $calendar->add_repeating_closure( { day => 4, month => 7, title => 'Independence', description => '' } );
+    $calendar->add_single_closure( { date => '2027-01-01', title => 'New Year', description => '' } );
+    $calendar->add_exception( { date => '2027-01-02', title => 'Special opening', description => '' } );
+
+    # Past-dated single closure and exception must not be copied
+    my $past_date = $today->clone->subtract( years => 1 )->ymd;
+    $calendar->add_single_closure( { date => $past_date, title => 'Past single', description => '' } );
+    $calendar->add_exception( { date => $past_date, title => 'Past exception', description => '' } );
+
+    my $library2 = $builder->build_object( { class => 'Koha::Libraries' } );
+    $calendar->copy_to( $library2->branchcode );
+
+    is(
+        Koha::Library::Calendar::WeeklyClosures->search( { library_id => $library2->branchcode } )->count, 1,
+        'Weekly closure copied'
+    );
+    is(
+        Koha::Library::Calendar::RepeatingClosures->search( { library_id => $library2->branchcode } )->count, 1,
+        'Repeating closure copied'
+    );
+    is(
+        Koha::Library::Calendar::SingleClosures->search( { library_id => $library2->branchcode } )->count, 1,
+        'Only the future single closure copied (past single excluded)'
+    );
+    is(
+        Koha::Library::Calendar::Exceptions->search( { library_id => $library2->branchcode } )->count, 1,
+        'Only the future exception copied (past exception excluded)'
+    );
+
+    # copy_to should not duplicate on a second run
+    $calendar->copy_to( $library2->branchcode );
+    is(
+        Koha::Library::Calendar::WeeklyClosures->search( { library_id => $library2->branchcode } )->count, 1,
+        'No duplicate weekly after second copy'
+    );
+    is(
+        Koha::Library::Calendar::RepeatingClosures->search( { library_id => $library2->branchcode } )->count, 1,
+        'No duplicate repeating after second copy'
+    );
+    is(
+        Koha::Library::Calendar::SingleClosures->search( { library_id => $library2->branchcode } )->count, 1,
+        'No duplicate single after second copy'
+    );
+    is(
+        Koha::Library::Calendar::Exceptions->search( { library_id => $library2->branchcode } )->count, 1,
+        'No duplicate exception after second copy'
+    );
+
+    $schema->storage->txn_rollback;
+};