diff --git a/tests/phpunit/tests/date/currentTime.php b/tests/phpunit/tests/date/currentTime.php
index c98292ef0d..4a56098c93 100644
--- a/tests/phpunit/tests/date/currentTime.php
+++ b/tests/phpunit/tests/date/currentTime.php
@@ -81,7 +81,7 @@ class Tests_Date_CurrentTime extends WP_UnitTestCase {
 	 * @ticket 40653
 	 */
 	public function test_should_return_wp_timestamp() {
-		update_option( 'timezone_string', 'Europe/Kiev' );
+		update_option( 'timezone_string', 'Europe/Helsinki' );
 
 		$timestamp = time();
 		$datetime  = new DateTime( '@' . $timestamp );
@@ -106,7 +106,7 @@ class Tests_Date_CurrentTime extends WP_UnitTestCase {
 	 * @ticket 40653
 	 */
 	public function test_should_return_correct_local_time() {
-		update_option( 'timezone_string', 'Europe/Kiev' );
+		update_option( 'timezone_string', 'Europe/Helsinki' );
 
 		$timestamp      = time();
 		$datetime_local = new DateTime( '@' . $timestamp );
diff --git a/tests/phpunit/tests/date/dateI18n.php b/tests/phpunit/tests/date/dateI18n.php
index 9279aca4eb..79598539cd 100644
--- a/tests/phpunit/tests/date/dateI18n.php
+++ b/tests/phpunit/tests/date/dateI18n.php
@@ -11,7 +11,7 @@ class Tests_Date_DateI18n extends WP_UnitTestCase {
 	 * @ticket 28636
 	 */
 	public function test_should_return_current_time_on_invalid_timestamp() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 
 		$datetime     = new DateTime( 'now', new DateTimeZone( $timezone ) );
@@ -24,7 +24,7 @@ class Tests_Date_DateI18n extends WP_UnitTestCase {
 	 * @ticket 28636
 	 */
 	public function test_should_handle_zero_timestamp() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 
 		$datetime = DateTimeImmutable::createFromFormat(
@@ -143,7 +143,7 @@ class Tests_Date_DateI18n extends WP_UnitTestCase {
 	 * @ticket 25768
 	 */
 	public function test_should_return_wp_timestamp() {
-		update_option( 'timezone_string', 'Europe/Kiev' );
+		update_option( 'timezone_string', 'Europe/Helsinki' );
 
 		$datetime     = new DateTimeImmutable( 'now', wp_timezone() );
 		$timestamp    = $datetime->getTimestamp();
@@ -193,10 +193,10 @@ class Tests_Date_DateI18n extends WP_UnitTestCase {
 
 	public function dst_times() {
 		return array(
-			'Before DST start' => array( '2019-03-31 02:59:00', 'Europe/Kiev' ),
-			'After DST start'  => array( '2019-03-31 04:01:00', 'Europe/Kiev' ),
-			'Before DST end'   => array( '2019-10-27 02:59:00', 'Europe/Kiev' ),
-			'After DST end'    => array( '2019-10-27 04:01:00', 'Europe/Kiev' ),
+			'Before DST start' => array( '2019-03-31 02:59:00', 'Europe/Helsinki' ),
+			'After DST start'  => array( '2019-03-31 04:01:00', 'Europe/Helsinki' ),
+			'Before DST end'   => array( '2019-10-27 02:59:00', 'Europe/Helsinki' ),
+			'After DST end'    => array( '2019-10-27 04:01:00', 'Europe/Helsinki' ),
 		);
 	}
 }
diff --git a/tests/phpunit/tests/date/getFeedBuildDate.php b/tests/phpunit/tests/date/getFeedBuildDate.php
index 23d97aa473..c5dcc7ce2f 100644
--- a/tests/phpunit/tests/date/getFeedBuildDate.php
+++ b/tests/phpunit/tests/date/getFeedBuildDate.php
@@ -47,7 +47,7 @@ class Tests_Date_GetFeedBuildDate extends WP_UnitTestCase {
 	public function test_should_fall_back_to_last_post_modified() {
 		global $wp_query;
 
-		update_option( 'timezone_string', 'Europe/Kiev' );
+		update_option( 'timezone_string', 'Europe/Helsinki' );
 		$datetime     = new DateTimeImmutable( 'now', wp_timezone() );
 		$datetime_utc = $datetime->setTimezone( new DateTimeZone( 'UTC' ) );
 
diff --git a/tests/phpunit/tests/date/getPostTime.php b/tests/phpunit/tests/date/getPostTime.php
index ad9eb0cf31..58cb4eb7fe 100644
--- a/tests/phpunit/tests/date/getPostTime.php
+++ b/tests/phpunit/tests/date/getPostTime.php
@@ -51,7 +51,7 @@ class Tests_Date_GetPostTime extends WP_UnitTestCase {
 	 * @ticket 25002
 	 */
 	public function test_should_return_wp_timestamp() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 
 		$datetime     = new DateTimeImmutable( 'now', new DateTimeZone( $timezone ) );
@@ -80,7 +80,7 @@ class Tests_Date_GetPostTime extends WP_UnitTestCase {
 	 * @ticket 25002
 	 */
 	public function test_should_return_time() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 
 		$datetime    = new DateTimeImmutable( 'now', new DateTimeZone( $timezone ) );
@@ -121,7 +121,7 @@ class Tests_Date_GetPostTime extends WP_UnitTestCase {
 			)
 		);
 
-		update_option( 'timezone_string', 'Europe/Kiev' );
+		update_option( 'timezone_string', 'Europe/Helsinki' );
 
 		$this->assertSame( $rfc3339, get_post_time( DATE_RFC3339, true, $post_id ) );
 		$this->assertSame( $rfc3339, get_post_modified_time( DATE_RFC3339, true, $post_id ) );
diff --git a/tests/phpunit/tests/date/mysql2date.php b/tests/phpunit/tests/date/mysql2date.php
index 7c83446b00..0054150a3e 100644
--- a/tests/phpunit/tests/date/mysql2date.php
+++ b/tests/phpunit/tests/date/mysql2date.php
@@ -33,7 +33,7 @@ class Tests_Date_mysql2date extends WP_UnitTestCase {
 	 * @ticket 28992
 	 */
 	public function test_mysql2date_should_format_time() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 		$datetime = new DateTime( 'now', new DateTimeZone( $timezone ) );
 		$rfc3339  = $datetime->format( DATE_RFC3339 );
@@ -47,7 +47,7 @@ class Tests_Date_mysql2date extends WP_UnitTestCase {
 	 * @ticket 28992
 	 */
 	public function test_mysql2date_should_format_time_with_changed_time_zone() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		// phpcs:ignore WordPress.DateTime.RestrictedFunctions.timezone_change_date_default_timezone_set
 		date_default_timezone_set( $timezone );
 		update_option( 'timezone_string', $timezone );
@@ -63,7 +63,7 @@ class Tests_Date_mysql2date extends WP_UnitTestCase {
 	 * @ticket 28992
 	 */
 	public function test_mysql2date_should_return_wp_timestamp() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 		$datetime     = new DateTime( 'now', new DateTimeZone( $timezone ) );
 		$wp_timestamp = $datetime->getTimestamp() + $datetime->getOffset();
@@ -77,7 +77,7 @@ class Tests_Date_mysql2date extends WP_UnitTestCase {
 	 * @ticket 28992
 	 */
 	public function test_mysql2date_should_return_unix_timestamp_for_gmt_time() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 		$datetime  = new DateTime( 'now', new DateTimeZone( 'UTC' ) );
 		$timestamp = $datetime->getTimestamp();
diff --git a/tests/phpunit/tests/date/query.php b/tests/phpunit/tests/date/query.php
index e3f4ba0f6f..95a9782c8d 100644
--- a/tests/phpunit/tests/date/query.php
+++ b/tests/phpunit/tests/date/query.php
@@ -561,7 +561,7 @@ class Tests_Date_Query extends WP_UnitTestCase {
 	 * @param bool         $default_to_max Flag to default missing values to max.
 	 */
 	public function test_build_mysql_datetime_with_custom_timezone( $datetime, $expected, $default_to_max = false ) {
-		update_option( 'timezone_string', 'Europe/Kiev' );
+		update_option( 'timezone_string', 'Europe/Helsinki' );
 
 		$q = new WP_Date_Query( array() );
 
@@ -583,7 +583,7 @@ class Tests_Date_Query extends WP_UnitTestCase {
 	 * @ticket 41782
 	 */
 	public function test_build_mysql_datetime_with_relative_date() {
-		update_option( 'timezone_string', 'Europe/Kiev' );
+		update_option( 'timezone_string', 'Europe/Helsinki' );
 
 		$q = new WP_Date_Query( array() );
 
diff --git a/tests/phpunit/tests/date/wpTimezone.php b/tests/phpunit/tests/date/wpTimezone.php
index 8b1f09e4d1..fdd369917b 100644
--- a/tests/phpunit/tests/date/wpTimezone.php
+++ b/tests/phpunit/tests/date/wpTimezone.php
@@ -31,13 +31,13 @@ class Tests_Date_wpTimezone extends WP_UnitTestCase {
 	 * @ticket 24730
 	 */
 	public function test_should_return_timezone_string() {
-		update_option( 'timezone_string', 'Europe/Kiev' );
+		update_option( 'timezone_string', 'Europe/Helsinki' );
 
-		$this->assertSame( 'Europe/Kiev', wp_timezone_string() );
+		$this->assertSame( 'Europe/Helsinki', wp_timezone_string() );
 
 		$timezone = wp_timezone();
 
-		$this->assertSame( 'Europe/Kiev', $timezone->getName() );
+		$this->assertSame( 'Europe/Helsinki', $timezone->getName() );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/date/xmlrpc.php b/tests/phpunit/tests/date/xmlrpc.php
index 8a4efaf46d..f00d88ff4c 100644
--- a/tests/phpunit/tests/date/xmlrpc.php
+++ b/tests/phpunit/tests/date/xmlrpc.php
@@ -24,7 +24,7 @@ class Tests_Date_XMLRPC extends WP_XMLRPC_UnitTestCase {
 			$this->expectDeprecationMessageMatches( '`Passing null to parameter \#[0-9]+ \(\$[^\)]+\) of type [^ ]+ is deprecated`' );
 		}
 
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 
 		$datetime    = new DateTimeImmutable( 'now', new DateTimeZone( $timezone ) );
@@ -144,7 +144,7 @@ class Tests_Date_XMLRPC extends WP_XMLRPC_UnitTestCase {
 	 * @covers wp_xmlrpc_server::mw_editPost
 	 */
 	public function test_date_edit_post() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 
 		$datetime    = new DateTimeImmutable( 'now', new DateTimeZone( $timezone ) );
@@ -213,7 +213,7 @@ class Tests_Date_XMLRPC extends WP_XMLRPC_UnitTestCase {
 	 * @covers wp_xmlrpc_server::wp_editComment
 	 */
 	public function test_date_edit_comment() {
-		$timezone = 'Europe/Kiev';
+		$timezone = 'Europe/Helsinki';
 		update_option( 'timezone_string', $timezone );
 
 		$datetime    = new DateTimeImmutable( 'now', new DateTimeZone( $timezone ) );
diff --git a/tests/phpunit/tests/formatting/date.php b/tests/phpunit/tests/formatting/date.php
index 9f0f975d4c..0b10c8da19 100644
--- a/tests/phpunit/tests/formatting/date.php
+++ b/tests/phpunit/tests/formatting/date.php
@@ -197,7 +197,7 @@ class Tests_Formatting_Date extends WP_UnitTestCase {
 	public function timezone_provider() {
 		return array(
 			array(
-				'timezone_string' => 'Europe/Kiev',
+				'timezone_string' => 'Europe/Helsinki',
 				'gmt_offset'      => 3,
 			),
 			array(