diff --git a/plugins/libkolab/skins/elastic/include/darkmode.less b/plugins/libkolab/skins/elastic/include/darkmode.less
new file mode 100644
index 00000000..3f018b2a
--- /dev/null
+++ b/plugins/libkolab/skins/elastic/include/darkmode.less
@@ -0,0 +1,168 @@
+/**
+ * Kolab core library
+ *
+ * This file contains Elastic skin dark mode styles for all Kolab plugins
+ *
+ * @author Aleksander Machniak <machniak@kolabsys.com>
+ *
+ * Copyright (C) 2012-2018, Kolab Systems AG <contact@kolabsys.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+html.dark-mode {
+    // Use icons-only on taskmenu with small screen height
+    @media screen and (max-height: 750px) and (min-width: (@screen-width-small + 1px)) {
+        #taskmenu a {
+            width: @layout-menu-width-sm - 1px;
+        }
+    }
+
+    .watermark {
+        background-color: @color-dark-background;
+        background-blend-mode: soft-light;
+
+        &:before {
+            background: none;
+        }
+    }
+
+    #filelistcontainer,
+    .fc-scroller {
+        scrollbar-width: thin;
+    }
+
+    .fc {
+        .fc-header-toolbar {
+            background-color: @color-dark-list-selected-background;
+        }
+
+        #timezone-display,
+        .fc-center h2 {
+            color: @color-dark-font;
+        }
+    }
+
+    .filelist tr.session.owner > td.name::after,
+    .rsvp-status:not(.accepted):not(.tentative):not(.declined)::before,
+    .resources-dialog .listing li.resource > a {
+        color: @color-dark-font;
+    }
+
+    .fc-unthemed th,
+    .fc-unthemed td,
+    .fc-unthemed .fc-divider,
+    .fc-unthemed .fc-row,
+    .fc-unthemed .fc-content,
+    .fc-unthemed .fc-popover,
+    .fc-unthemed .fc-list-view,
+    .fc-unthemed .fc-list-heading td,
+    #tasklist li.taskitem > div,
+    #tasklist li.taskitem > span {
+        border-color: @color-dark-list-border;
+    }
+
+    .files-dialog .selection-content,
+    .calendar-scheduler .schedule-table td.times td,
+    .calendar-scheduler .attendees-list div.attendee,
+    .calendar-scheduler .schedule-table .timesheader,
+    .calendar-scheduler .schedule-table td.attendees .attendees-list,
+    .fc-unthemed th,
+    .fc-unthemed td {
+        border-color: @color-dark-border;
+    }
+
+    #resource-availability .fc,
+    #resource-availability .fc-view {
+        border-color: @color-dark-border;
+    }
+
+    .selection-dialog .form-addon,
+    .selection-dialog .header,
+    .selection-dialog .selection-list,
+    .edit-attendees-table th {
+        border-color: @color-dark-border !important;
+    }
+
+    .selection-dialog .listing ul,
+    .selection-dialog .form-addon,
+    .selection-dialog .header {
+        background-color: transparent;
+    }
+
+    .fc-unthemed .fc-divider,
+    .fc-unthemed .fc-popover .fc-header,
+    .fc-unthemed .fc-list-heading td,
+    body.task-calendar .ui-datepicker-inline .ui-datepicker-activerange,
+    .listing li.selected > div > *,
+    #tasklist li.taskitem div.taskhead.selected {
+        color: @color-dark-list-selected;
+        background-color: @color-dark-list-selected-background;
+    }
+
+    #folder-mount-form td.source.selected {
+        background-color: @color-dark-list-selected-background;
+    }
+
+    #tagsform option,
+    .tagedit-list li.tagedit-listelement-new input {
+        color: @color-dark-input;
+    }
+
+    .fc .fc-axis,
+    .fc .fc-day-number,
+    .fc .fc-week-number,
+    .fc .fc-day-header,
+    .fc .fc-week-header,
+    .formcontent.text-only .faded *,
+    .availability span,
+    .invitebox td.label,
+    .invitebox .rsvp-status.hint,
+    .calendar-agenda-preview .event-row.current,
+    #tasklist span.date,
+    #kolabnoteslist td.date,
+    #notedetailstitle .dates {
+        color: @color-dark-hint;
+    }
+
+    .invitebox .folder-select select {
+        background-color: @color-dark-input-background;
+    }
+
+    .tagedit-list[tabindex="-1"] {
+        border-color: @color-dark-input-border-focus;
+        box-shadow: 0 0 0 .2rem @color-input-border-focus-shadow;
+        background: @color-dark-input-background-focus;
+    }
+
+    #tasklist .progressbar .progressvalue {
+        border-color: @color-dark-warning;
+    }
+
+    .listing {
+        li > div.readonly a:first-child,
+        li.readonly:not(.virtual) > div a:first-child {
+            &:after {
+                color: @color-dark-font;
+                background-color: @color-dark-background;
+            }
+        }
+    }
+
+    .dialog-message {
+        opacity: 1;
+        color: @color-dark-font;
+        background-color: @color-dark-warning;
+    }
+}
diff --git a/plugins/libkolab/skins/elastic/include/kolab_tags.less b/plugins/libkolab/skins/elastic/include/kolab_tags.less
index 527c84bf..71f6b7bc 100644
--- a/plugins/libkolab/skins/elastic/include/kolab_tags.less
+++ b/plugins/libkolab/skins/elastic/include/kolab_tags.less
@@ -1,123 +1,116 @@
 /**
  * Kolab core library
  *
  * This file contains Elastic skin style of kolab_tags plugin.
  *
  * @author Aleksander Machniak <machniak@kolabsys.com>
  *
  * Copyright (C) 2012-2018, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program 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 Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 .menu {
     a.tags:before {
         content: @fa-var-tags;
     }
 
     a.tag:before,
     a.tag.remove:before,
     a.tag.remove.all:before {
         content: @fa-var-tag;
     }
 }
 
 #taglist {
     li {
         padding: 0 .5rem;
 
         &:before {
             &:extend(.font-icon-class);
             content: @fa-var-tag;
             margin: 0 .5rem 0 .2rem;
         }
     }
 }
 
 #tagsform option:before,
 #taglist li:before,
 #tag-selector li a:before {
     color: darken(@color-main, 15%); // default tag color
 }
 
 #tagsform option:checked:before,
 #tag-selector li:hover a:before {
     color: #fff;
 }
 
 #tagsform {
     min-height: 15rem;
 
     select {
         padding: 0;
         margin-bottom: .5rem;
-
-        &:focus {
-            box-shadow: none !important;
-            border: 1px solid @color-layout-border;
-        }
     }
 
     option {
-        color: @color-font; // fix Firefox issue caused by text-shadow below
-        text-shadow: none;
         padding: .5rem;
         outline: 0;
         border: 0;
 
         &:before {
             &:extend(.font-icon-class);
             content: @fa-var-tag;
             line-height: 1;
         }
     }
 
     .buttons {
         text-align: center;
 
         button {
             margin: 0 .25rem;
         }
     }
 }
 
 .tagbox {
     color: #fff;
     background-color: @color-main !important;
     border: 0 !important;
     border-radius: .25rem;
     max-width: 4em;
     padding: .1rem .4rem;
     margin-right: .2rem;
     font-weight: bold;
 
     &:not(.tagedit-listelement) a {
         color: inherit;
         padding-left: .5rem;
         text-decoration: none;
     }
 
     h2 > & {
         font-size: 1.2rem;
     }
 }
 
 .tag-droppable.formcontainer {
     &.ui-droppable-active {
         background-color: @color-black-shade-bg !important;
     }
     &.ui-droppable-hover {
         background-color: @color-list-droptarget-background !important;
     }
 }
diff --git a/plugins/libkolab/skins/elastic/libkolab.less b/plugins/libkolab/skins/elastic/libkolab.less
index adc30425..8481910e 100644
--- a/plugins/libkolab/skins/elastic/libkolab.less
+++ b/plugins/libkolab/skins/elastic/libkolab.less
@@ -1,622 +1,623 @@
 /**
  * Kolab core library
  *
  * This file contains Elastic skin styles for various Kolab plugins.
  *
  * @author Aleksander Machniak <machniak@kolabsys.com>
  *
  * Copyright (C) 2012-2018, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program 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 Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 @skin: "elastic";
 @skin-path: "../../../../skins/@{skin}";
 
 @import (reference) "@{skin-path}/styles/variables";
 @import (reference) "@{skin-path}/styles/mixins";
 
 
 /*** Common folders list extensions ***/
 
 .listing {
     // Fix focus indicator, because we add div element in the list record
     @media screen and (min-width: @screen-width-large) {
         li > div > a {
             border-left: 2px solid transparent;
         }
         li > div > a:focus {
             border-left: 2px solid @color-list-focus-indicator;
             outline: 0;
         }
     }
 
     li {
         & > div {
             display: flex;
 
             & > a:first-child {
                 .overflow-ellipsis;
                 position: relative;
                 flex-grow: 1;
 
                 & + input {
                     position: initial;
                 }
             }
 
             .custom-switch {
                 position: relative;
             }
 
             &.folder .listname:before {
                 &:extend(.font-icon-class);
                 content: @fa-var-sticky-note;
                 margin-right: .5rem;
             }
 
             span.actions {
                 display: flex;
 
                 input + & {
                     padding-right: 2em;
                 }
 
                 a {
                     padding: 0;
                     margin: 0;
                     margin-right: .2rem;
                     cursor: pointer;
 
                     &:before {
                         margin: 0;
                     }
 
                     &.remove {
                         display: none;
                     }
                 }
 
                 html.touch & {
                     padding-left: .2rem;
                     a {
                         margin-right: .5rem;
                     }
                 }
             }
 
             a.quickview {
                 &:before {
                     content: @fa-var-eye;
                     opacity: .2;
                     color: @color-link;
                 }
 
                 &:after {
                     display: none !important;
                 }
             }
 
             &.focusview {
                 a.quickview:before {
                     content: @fa-var-eye;
                     opacity: 1;
                 }
             }
 
             .subscribed {
                 cursor: pointer;
                 // reset listing's link style
                 padding: 0 !important;
                 border-left: 0;
                 width: auto;
 
                 &:before {
                     .font-icon-regular(@fa-var-bookmark); // TODO: better icon
                     height: auto;
                     color: @color-link;
                     margin-right: .25rem;
                 }
             }
 
             // span.subscribed is used on addressbooks list, a.subscribed in other places
             span.subscribed:before {
                 &:extend(.font-icon-class);
                 .font-icon-regular(@fa-var-bookmark); // TODO: better icon
             }
 
             &.subscribed {
                 .subscribed:before {
                     .font-icon-solid(@fa-var-bookmark); // TODO: better icon
                 }
             }
         }
 
         &.selected > div > * {
             color: @color-list-selected;
             background-color: @color-list-selected-background;
         }
 
         & > div.readonly a:first-child,
         &.readonly:not(.virtual) > div a:first-child {
             &:after {
                 &:extend(.font-icon-class);
                 content: @fa-var-lock;
                 position: absolute;
                 left: 2.25rem;
                 top: @listing-line-height / 2;
                 font-size: .9em !important;
                 width: .9em;
                 line-height: 1;
                 height: 1em !important;
                 background-color: #fff;
                 border-radius: 50% 50% 0 0;
                 color: @color-font;
                 opacity: .9;
 
                 html.touch & {
                     top: @listing-touch-line-height / 2;
                     left: 2.7rem;
                 }
             }
         }
 
         & > div.other.user > .listname,
         &.other.user > div a:first-child {
             &:before {
                 .font-icon-solid(@fa-var-user);
             }
         }
 
         & > div.virtual.user > .listname,
         &.virtual.user > div a:first-child {
             &:after {
                 display: none;
             }
         }
 
         & > div.virtual.shared > .listname,
         &.virtual.shared > div a:first-child {
             &:before {
                 .font-icon-solid(@fa-var-share-alt);
             }
 
             &:after {
                 display: none;
             }
         }
 
         &.virtual > div > a {
             opacity: .5;
         }
     }
 
     // Tree structure fix
     &.treelist:not(.notree) {
         & > li > div > a {
             padding-left: @listing-treetoggle-width;
         }
     }
 
     li.droptarget > div {
         background-color: @color-list-droptarget-background;
     }
 
     li .count {
         position: absolute;
         top: 0;
         right: 0;
         min-width: 2em;
         line-height: 1.4rem;
         margin: (@listing-line-height - 1.4 * @page-font-size)/2;
         padding: 0 .3em;
         border-radius: .4em;
         background: @color-list-secondary;
         color: #fff;
         text-align: center;
         font-weight: bold;
 
         html.touch & {
             line-height: 2rem;
             margin: (@listing-touch-line-height - 2 * @page-font-size)/2;
         }
     }
 }
 
 @treelist-readonly-icon-margin: 1.7em;
 .treelist {
     ul {
         li {
             a:first-child:after {
                 margin-left: 1 * @treelist-readonly-icon-margin !important;
             }
 
             li {
                 a:first-child:after {
                     margin-left: 2 * @treelist-readonly-icon-margin !important;
                 }
 
                 li {
                     a:first-child:after {
                         margin-left: 3 * @treelist-readonly-icon-margin !important;
                     }
 
                     li {
                         a:first-child:after {
                             margin-left: 4 * @treelist-readonly-icon-margin !important;
                         }
 
                         li {
                             a:first-child:after {
                                 margin-left: 5 * @treelist-readonly-icon-margin !important;
                             }
 
                             li {
                                 a:first-child:after {
                                     margin-left: 6 * @treelist-readonly-icon-margin !important;
                                 }
                             }
                         }
                     }
                 }
             }
         }
     }
 
     &.notree {
         li a:first-child:after {
             left: 1.3rem !important;
         }
     }
 }
 
 .searchresults {
     .boxtitle {
         line-height: 2rem !important;
         font-size: 80%;
         padding: 0 .5rem;
         margin: 0;
         color: @color-popover-separator;
         background-color: @color-popover-separator-background;
         text-align: center;
         border-bottom: 1px solid @color-layout-border;
     }
 }
 
 .folderlist li.mailbox {
     &.type-event > a:before {
         .font-icon-solid(@fa-var-calendar);
     }
     &.type-task > a:before {
         .font-icon-solid(@fa-var-calendar-check);
     }
     &.type-journal > a:before {
         .font-icon-regular(@fa-var-calendar);
     }
     &.type-contact > a:before {
         .font-icon-regular(@fa-var-address-book);
     }
     &.type-note > a:before {
         .font-icon-regular(@fa-var-sticky-note);
     }
     &.type-configuration > a:before {
         .font-icon-solid(@fa-var-cog);
     }
     &.type-freebusy > a:before {
         .font-icon-regular(@fa-var-calendar);
     }
     &.type-file > a:before {
         .font-icon-solid(@fa-var-folder);
     }
 }
 
 .menu {
     li.search {
         padding: .25rem .5rem;
     }
 
     a.history:before {
         content: @fa-var-history;
     }
 }
 
 button.btn {
     &.save.notify:before {
         content: @fa-var-envelope;
     }
 
     &.print:before {
         content: @fa-var-print;
     }
 }
 
 // E.g. notes preview frame
 .watermark {
     background: url("@{skin-path}/images/logo.svg") center no-repeat #fff;
     background-size: 30%;
     background-blend-mode: luminosity;
     width: 100%;
     height: 100%;
 
     & > * {
         display: none;
     }
 
     // this is to blend the watermark image
     &:before {
         content: "";
         position: absolute;
         top: 0;
         bottom: 0;
         left: 0;
         right: 0;
         background: rgba(255, 255, 255, .85);
     }
 
     &.formcontainer {
         background: transparent !important;
 
         &:before {
             display: none;
         }
 
         & > * {
             display: block;
         }
 
         html.layout-small &,
         html.layout-phone & {
             overflow-y: auto !important;
         }
     }
 }
 
 .form-group > .datetime {
     display: flex;
     white-space: nowrap;
 
     input {
         width: 10em;
     }
 
     input:first-child {
         margin-right: .5rem;
         width: 15em;
     }
 
     a {
         margin-left: 1em;
         text-align: right;
         flex: 1;
         line-height: 2.4;
     }
 }
 
 .form-section.form-group.form-check {
     display: flex;
     padding: 0;
 
     label {
         order: 10;
     }
 }
 
 .formcontent.text-only .faded * {
     color: @color-black-shade-text;
 }
 
 .linkslist {
     // Reset .attachmentslist style
     border: 0 !important;
     background: transparent !important;
 
     li.link {
         padding: 0;
 
         &.message.eml:before {
             content: @fa-var-envelope;
         }
 
         a.messagelink {
             .overflow-ellipsis;
         }
 
         a.delete .inner {
             display: none;
         }
     }
 }
 
 .print-config {
     position: fixed;
     top: 0;
     left: 0;
     width: 100%;
     z-index: 10000;
     padding: .5em 1em;
     background-color: @color-black-shade-bg;
 
     button.print {
         margin-right: 1rem;
     }
 
     .prop {
         line-height: 2;
         margin-left: .5rem;
         display: inline-block;
         vertical-align: middle;
 
         label {
             margin: 0;
         }
     }
 
     @media print {
         display: none;
     }
 
     & + .print-content {
         position: relative;
         top: 0;
         left: 0;
         height: auto;
         margin: 5em auto 0 auto;
         overflow: visible;
     }
 }
 
 .selection-dialog {
     .ui-dialog-content {
         display: flex !important;
         overflow: hidden !important;
     }
 
     .selection-list {
         display: flex;
         flex-direction: column;
         border: 1px solid @color-layout-border;
         justify-content: center;
     }
 
     .ui-dialog-content .popupmenu {
         display: flex !important; // overwrites .popupmenu style
         width: 100%;
     }
 
     .scroller {
         flex: 1;
         overflow-y: auto;
     }
 
     .header {
         border-bottom: 1px solid @color-layout-border;
         display: flex;
         background-color: @color-layout-header-background;
         font-size: @layout-header-font-size;
         font-weight: bold;
         line-height: @layout-header-height;
         height: @layout-header-height;
         min-height: @layout-header-height;
         padding: 0 .25em;
         position: relative; // for absolute positioning of searchbar
         overflow: hidden;
         white-space: nowrap;
 
         a.button {
             color: @color-toolbar-button;
             margin: 0 .3rem;
 
             &:before {
                 margin: 0;
             }
         }
     }
 
     .header-title {
         width: 100%;
         text-align: center;
         margin: 0 2em;
     }
 
     .selection-content {
         display: flex;
         flex-direction: column;
     }
 
     .tab-content {
         margin-top: 1rem;
         height: 100%;
         overflow-y: auto;
     }
 
     .form-addon {
         margin: 0;
         padding: .5rem 0;
         width: 100%;
         background-color: @color-black-shade-bg;
         border-top: 1px solid @color-layout-border;
     }
 
     // overwrite .popupmenu colors
     .listing {
         ul {
             background-color: @color-layout-list-background;
         }
 
         li.selected {
             color: @color-font;
         }
     }
 
     @media screen and (max-width: @screen-width-small) {
         .ui-dialog-content {
             padding: 0 !important;
         }
 
         .ui-dialog-titlebar {
             display: none;
             margin: 0;
         }
 
         .selection-list {
             border: 0;
         }
 
         .selection-list,
         .selection-content {
             .header-title {
                 margin-left: 0;
             }
         }
 
         .header {
             a:before {
                 font-size: 1.75rem;
             }
         }
     }
 }
 
 // Use icons-only on taskmenu with small screen height
-@media screen and (max-height: 640px) and (min-width: (@screen-width-small + 1px)) {
+@media screen and (max-height: 750px) and (min-width: (@screen-width-small + 1px)) {
     #layout-menu .popover-header img,
     #layout-menu {
         width: @layout-menu-width-sm;
     }
 
     #taskmenu {
         a {
             height: @layout-menu-width-sm;
-            width: 100%;
+            width: @layout-menu-width-sm;
             font-size: 1.2rem !important;
         }
 
         .special-buttons {
             width: @layout-menu-width-sm;
         }
 
         span.inner {
             display: none;
         }
     }
 }
 
 @import "include/calendar";
 @import "include/kolab_activesync";
 @import "include/kolab_delegation";
 @import "include/kolab_files";
 @import "include/kolab_notes";
 @import "include/kolab_tags";
 @import "include/libcalendaring";
 @import "include/tasklist";
+@import "include/darkmode";