diff --git a/test/list_volumes_test.pm b/test/list_volumes_test.pm
index efcb547..02edc35 100644
--- a/test/list_volumes_test.pm
+++ b/test/list_volumes_test.pm
@@ -130,7 +130,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1585595500,
+		'ctime'   => 1585602700,
 		'format'  => 'vma.gz',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '16110',
@@ -138,7 +138,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1585595565,
+		'ctime'   => 1585602765,
 		'format'  => 'vma.lzo',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '16110',
@@ -146,7 +146,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1585595635,
+		'ctime'   => 1585602835,
 		'format'  => 'vma',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '16110',
@@ -154,7 +154,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1585595635,
+		'ctime'   => 1585602835,
 		'format'  => 'vma.zst',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '16110',
@@ -199,7 +199,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1585597170,
+		'ctime'   => 1585604370,
 		'format'  => 'tar.lzo',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '16112',
@@ -207,7 +207,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1585597770,
+		'ctime'   => 1585604970,
 		'format'  => 'tar.gz',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '16112',
@@ -215,7 +215,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1585597770,
+		'ctime'   => 1585604970,
 		'format'  => 'tar.zst',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '16112',
@@ -223,7 +223,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1585598370,
+		'ctime'   => 1585605570,
 		'format'  => 'tgz',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '16112',
@@ -365,7 +365,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1580756263,
+		'ctime'   => 1580759863,
 		'format'  => 'tar.gz',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '19253',
@@ -373,7 +373,7 @@ my @tests = (
 	    },
 	    {
 		'content' => 'backup',
-		'ctime'   => 1548095359,
+		'ctime'   => 1548098959,
 		'format'  => 'tar',
 		'size'    => DEFAULT_SIZE,
 		'vmid'    => '19254',
diff --git a/test/run_plugin_tests.pl b/test/run_plugin_tests.pl
index e29fc88..54322bb 100755
--- a/test/run_plugin_tests.pl
+++ b/test/run_plugin_tests.pl
@@ -3,6 +3,9 @@
 use strict;
 use warnings;
 
+# to ensure consistent ctime values on all systems
+$ENV{TZ} = 'UTC';
+
 use TAP::Harness;
 
 my $harness = TAP::Harness->new( { verbosity => -1 });