diff --git a/config.js b/config.js
index d75841e..a0dbf45 100644
--- a/config.js
+++ b/config.js
@@ -1,14 +1,19 @@
 /* Application configuration
- * debug      - Show debug panel (0/1)
- * theme      - Color palette: 'ash', 'gruvbox' or 'nord'
- * units      - Measurement units: 'metric' or 'imperial'
- * language   - UI language: 'de' or 'en'
+ * debug       - Show debug panel (0/1)
+ * theme       - Color palette: 'ash', 'gruvbox' or 'nord'
+ * units       - Measurement units: 'metric' or 'imperial'
+ * language    - UI language: 'de' or 'en'
+ * timeFormat  - ISO-8601-ish format string for the digital clock.
+ *               Date-only: YYYY, YYYY-MM, YYYY-MM-DD
+ *               Date-time: above + T + HH:mm, HH:mm:ss, HH:mm:ss.sss
+ *               Optional timezone offset (e.g. +02:00)
  */
 window.CONFIG = {
     debug: 1,
     theme: 'ash',
     units: 'metric',
-    language: 'en'
+    language: 'en',
+    timeFormat: 'HH:mm:ss'
 };
 
 // List of available themes. The key is the theme id (used in config.theme),
diff --git a/index.html b/index.html
index c0d93af..782497d 100644
--- a/index.html
+++ b/index.html
@@ -808,6 +808,47 @@ var effect = (VANTA.CLOUDS2 || VANTA.CLOUDS)({
             return (h < 10 ? '0' : '') + h + ':' + (m < 10 ? '0' : '') + m + ':' + (s < 10 ? '0' : '') + s;
         }
 
+        function pad2(n) { return n < 10 ? '0' + n : '' + n; }
+        function pad3(n) { return n < 10 ? '00' + n : n < 100 ? '0' + n : '' + n; }
+
+        function formatDateTime(format, date) {
+            // Parse ISO-8601-ish format string and replace tokens with date values
+            var result = '';
+            var i = 0;
+            while (i < format.length) {
+                var ch = format.charAt(i);
+                if (ch === 'Y' && format.substr(i, 4) === 'YYYY') {
+                    result += date.getFullYear();
+                    i += 4;
+                } else if (ch === 'Y') {
+                    result += date.getFullYear();
+                    i += 1;
+                } else if (ch === 'M' && format.substr(i, 2) === 'MM') {
+                    result += pad2(date.getMonth() + 1);
+                    i += 2;
+                } else if (ch === 'D' && format.substr(i, 2) === 'DD') {
+                    result += pad2(date.getDate());
+                    i += 2;
+                } else if (ch === 'H' && format.substr(i, 2) === 'HH') {
+                    result += pad2(date.getHours());
+                    i += 2;
+                } else if (ch === 'm' && format.substr(i, 2) === 'mm') {
+                    result += pad2(date.getMinutes());
+                    i += 2;
+                } else if (ch === 's' && format.substr(i, 2) === 'ss') {
+                    result += pad2(date.getSeconds());
+                    i += 2;
+                } else if (ch === 's' && format.substr(i, 3) === 'sss') {
+                    result += pad3(date.getMilliseconds());
+                    i += 3;
+                } else {
+                    result += ch;
+                    i += 1;
+                }
+            }
+            return result;
+        }
+
         function formatDateShort(date) {
             var d = date.getDate();
             var mo = date.getMonth() + 1;
@@ -1020,7 +1061,7 @@ var effect = (VANTA.CLOUDS2 || VANTA.CLOUDS)({
             var m = now.getMinutes();
             var s = now.getSeconds();
 
-            document.getElementById('digital-clock').textContent = formatTimeHMS(h, m, s);
+            document.getElementById('digital-clock').textContent = formatDateTime((window.CONFIG && window.CONFIG.timeFormat) || 'HH:mm:ss', now);
 
             var hourAngle = ((h % 12) + m / 60) * 30;
             var minuteAngle = (m + s / 60) * 6;