diff --git a/C4/Context.pm b/C4/Context.pm
index 07e81854bd..7ce91b6b35 100644
--- a/C4/Context.pm
+++ b/C4/Context.pm
@@ -97,6 +97,7 @@ use POSIX ();
 use DateTime::TimeZone;
 use Module::Load::Conditional qw(can_load);
 use Carp;
+use DateTime::TimeZone;
 
 use C4::Boolean;
 use C4::Debug;
@@ -981,6 +982,10 @@ sub timezone {
     my $self = shift;
 
     my $timezone = C4::Context->config('timezone') || $ENV{TZ} || 'local';
+    if ( !DateTime::TimeZone->is_valid_name( $timezone ) ) {
+        warn "Invalid timezone in koha-conf.xml ($timezone)";
+        $timezone = 'local';
+    }
 
     return $timezone;
 }
diff --git a/about.pl b/about.pl
index 91292a5a79..7ea8acd073 100755
--- a/about.pl
+++ b/about.pl
@@ -23,6 +23,7 @@
 use Modern::Perl;
 
 use CGI qw ( -utf8 );
+use DateTime::TimeZone;
 use List::MoreUtils qw/ any /;
 use LWP::Simple;
 use XML::Simple;
@@ -61,10 +62,31 @@ my ( $template, $loggedinuser, $cookie ) = get_template_and_user(
     }
 );
 
+my $config_timezone = C4::Context->config('timezone');
+my $config_invalid  = !DateTime::TimeZone->is_valid_name( $config_timezone );
+my $env_timezone    = $ENV{TZ};
+my $env_invalid     = !DateTime::TimeZone->is_valid_name( $env_timezone );
+my $actual_bad_tz_fallback = 0;
+
+if ( $config_timezone ne '' &&
+     $config_invalid ) {
+    # Bad config
+    $actual_bad_tz_fallback = 1;
+}
+elsif ( $config_timezone eq '' &&
+        $env_timezone    ne '' &&
+        $env_invalid ) {
+    # No config, but bad ENV{TZ}
+    $actual_bad_tz_fallback = 1;
+}
+
 my $time_zone = {
-    actual      => C4::Context->timezone(),
-    config      => C4::Context->config('timezone'),
-    environment => $ENV{TZ},
+    actual                 => C4::Context->timezone(),
+    actual_bad_tz_fallback => $actual_bad_tz_fallback,
+    config                 => $config_timezone,
+    config_invalid         => $config_invalid,
+    environment            => $env_timezone,
+    environment_invalid    => $env_invalid
 };
 $template->param( 'time_zone' => $time_zone );
 
diff --git a/koha-tmpl/intranet-tmpl/prog/en/modules/about.tt b/koha-tmpl/intranet-tmpl/prog/en/modules/about.tt
index b47423385a..e109eb0e33 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/modules/about.tt
+++ b/koha-tmpl/intranet-tmpl/prog/en/modules/about.tt
@@ -112,10 +112,24 @@
             <tr><th scope="row"><b>Warning</b> </th><td>Error message from Zebra: [% ( errZebraConnection ) %] </td></tr>
             [% END %]
             <tr>
+              [% timezone_config_class = (time_zone.config_invalid) ? 'status_warn' : '' %]
+              [% timezone_env_class    = (time_zone.env_invalid)    ? 'status_warn' : '' %]
               <th scope="row">Time zone: </th>
-              <td>Used: <span class="status_ok">[% time_zone.actual %]</span> |
-                  Config: [% IF time_zone.config != '' %][% time_zone.config %][% ELSE %]<span>Undefined</span>[% END %] |
-                  ENV: [% IF time_zone.environment != '' %][% time_zone.environment %][% ELSE %]<span>Undefined</span>[% END %]
+              <td>Used: <span>[% time_zone.actual %]</span>
+                          [% IF time_zone.actual_bad_tz_fallback %]
+                             <span>(This is a fallback value due to a bad configuration)</span>
+                          [% END %]
+                           |
+                  Config: [% IF time_zone.config != '' %]
+                            <span class="[% timezone_config_class %]">[% time_zone.config %]</span>
+                          [% ELSE %]
+                            <span>Undefined</span>
+                          [% END %] |
+                  Environment (TZ):  [% IF time_zone.environment != '' %]
+                          <span class="[% timezone_env_class %]">[% time_zone.environment %]</span>
+                        [% ELSE %]
+                          <span>Undefined</span>
+                        [% END %]
               </td>
             </tr>
         </table>
diff --git a/t/timezones.t b/t/timezones.t
index c5463dab90..ee64438852 100644
--- a/t/timezones.t
+++ b/t/timezones.t
@@ -2,9 +2,12 @@ use Modern::Perl;
 
 use C4::Context;
 
-use Test::More tests => 3;
+use Test::More tests => 5;
+use Test::Warn;
 use t::lib::Mocks;
 
+use DateTime::TimeZone;
+
 $ENV{TZ} = q{};
 t::lib::Mocks::mock_config( 'timezone', q{} );
 is( C4::Context->timezone, 'local',
@@ -23,3 +26,9 @@ is(
     'Antarctica/South_Pole',
     'Got correct timezone using config, overrides env'
 );
+
+t::lib::Mocks::mock_config( 'timezone', 'Your/Timezone' );
+warning_is {
+    is( C4::Context->timezone, 'local', 'Invalid timezone falls back to local' ); }
+    'Invalid timezone in koha-conf.xml (Your/Timezone)',
+    'Invalid timezone raises a warning';