diff --git a/background/color-scheme.js b/background/color-scheme.js
new file mode 100644
index 00000000..832e1c4f
--- /dev/null
+++ b/background/color-scheme.js
@@ -0,0 +1,93 @@
+/* global prefs */
+/* exported colorScheme */
+
+'use strict';
+
+const colorScheme = (() => {
+  let systemPreferDark = false;
+  let timePreferDark = false;
+  const changeListeners = new Set();
+
+  const media = window.matchMedia('(prefers-color-scheme: dark)');
+  media.addListener(updateSystemPreferDark);
+
+  const checkTime = ['schemeSwitcher.nightStart', 'schemeSwitcher.nightEnd'];
+  prefs.subscribe(checkTime, (key, value) => {
+    updateTimePreferDark();
+    createAlarm(key, value);
+  });
+  checkTime.forEach(key => createAlarm(key, prefs.get(key)));
+
+  prefs.subscribe(['schemeSwitcher.enabled'], emitChange);
+
+  updateSystemPreferDark();
+  updateTimePreferDark();
+
+  return {shouldIncludeStyle, onChange};
+
+  function createAlarm(key, value) {
+    const date = new Date();
+    applyDate(date, value);
+    if (date.getTime() < Date.now()) {
+      date.setDate(date.getDate() + 1);
+    }
+    chrome.alarms.create(key, {
+      when: date.getTime(),
+      periodInMinutes: 24 * 60
+    });
+  }
+
+  function shouldIncludeStyle(style) {
+    if (style.preferScheme === 'always') {
+      return true;
+    }
+    if (prefs.get('schemeSwitcher.enabled') === 'never') {
+      return true;
+    }
+    if (prefs.get('schemeSwitcher.enabled') === 'system') {
+      return systemPreferDark && style.preferScheme === 'dark' ||
+        !systemPreferDark && style.preferScheme === 'light';
+    }
+    return timePreferDark && style.preferScheme === 'dark' ||
+      !timePreferDark && style.preferScheme === 'light';
+  }
+
+  function updateSystemPreferDark() {
+    const oldValue = systemPreferDark;
+    systemPreferDark = media.matches;
+    if (systemPreferDark !== oldValue) {
+      emitChange();
+    }
+  }
+
+  function updateTimePreferDark() {
+    const oldValue = timePreferDark;
+    const date = new Date();
+    const now = date.getTime();
+    applyDate(date, prefs.get('schemeSwitcher.nightStart'));
+    const start = date.getTime();
+    applyDate(date, prefs.get('schemeSwitcher.nightEnd'));
+    const end = date.getTime();
+    timePreferDark = start > end ?
+      now >= start || now < end :
+      now >= start && now < end;
+    if (timePreferDark !== oldValue) {
+      emitChange();
+    }
+  }
+
+  function applyDate(date, time) {
+    const [h, m] = time.split(':').map(Number);
+    date.setHours(h, m, 0, 0);
+  }
+
+  function onChange(listener) {
+    changeListeners.add(listener);
+  }
+
+  function emitChange() {
+    for (const listener of changeListeners) {
+      listener();
+    }
+  }
+})();
diff --git a/background/style-manager.js b/background/style-manager.js
index d75d7b3f..d8a68c05 100644
--- a/background/style-manager.js
+++ b/background/style-manager.js
@@ -1,6 +1,6 @@
 /* eslint no-eq-null: 0, eqeqeq: [2, "smart"] */
 /* global createCache db calcStyleDigest db tryRegExp styleCodeEmpty
-  getStyleWithNoCode msg */
+  getStyleWithNoCode msg colorScheme */
 /* exported styleManager */
 'use strict';
 
@@ -479,6 +479,9 @@ const styleManager = (() => {
     if (!style.enabled) {
       return 'disabled';
     }
+    if (!colorScheme.shouldIncludeStyle(style)) {
+      return 'excludedScheme';
+    }
     return true;
   }
 
diff --git a/js/prefs.js b/js/prefs.js
index 03cbd31f..f7b84774 100644
--- a/js/prefs.js
+++ b/js/prefs.js
@@ -14,6 +14,10 @@ const prefs = (() => {
     // checkbox in style config dialog
     'config.autosave': true,
 
+    'schemeSwitcher.enabled': 'never',
+    'schemeSwitcher.nightStart': '18:00',
+    'schemeSwitcher.nightEnd': '06:00',
+
     'popup.breadcrumbs': true,      // display 'New style' links as URL breadcrumbs
     'popup.breadcrumbs.usePath': false, // use URL path for 'this URL'
     'popup.enabledFirst': true,     // display enabled styles before disabled styles
diff --git a/manifest.json b/manifest.json
index 385f9663..696f8837 100644
--- a/manifest.json
+++ b/manifest.json
@@ -37,6 +37,7 @@
       "js/cache.js",
       "background/content-scripts.js",
       "background/db.js",
+      "background/color-scheme.js",
       "background/style-manager.js",
       "background/navigator-util.js",
       "background/icon-util.js",