diff --git a/CHANGELOG.md b/CHANGELOG.md
index 89d4d892b..7770750e5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Fixed all dates to actually adhere to "Keep a changelog".
+- Fixed locale formatting for dates to adhere to UKEs writing rules.
+
+### Added
+
+- Added missing developer tab for date and time.
 
 ### Changed
 
diff --git a/src/general/helpers/date_and_time/date_and_time.html b/src/general/helpers/date_and_time/date_and_time.html
index 06f94b838..1cfe5d448 100644
--- a/src/general/helpers/date_and_time/date_and_time.html
+++ b/src/general/helpers/date_and_time/date_and_time.html
@@ -63,3 +63,11 @@ <h2 class="ods-infobox__heading">Important</h2>
     </div>
   </div>
 </div>
+
+<div class="ods-devtools-devmode">
+  <div class="ods-grid">
+    <div class="ods-grid__column--12">
+      <div id="testcases"></div>
+    </div>
+  </div>
+</div>
diff --git a/src/general/helpers/date_and_time/date_and_time.init.js b/src/general/helpers/date_and_time/date_and_time.init.js
index 6b7d0d2a8..5fbfe1759 100644
--- a/src/general/helpers/date_and_time/date_and_time.init.js
+++ b/src/general/helpers/date_and_time/date_and_time.init.js
@@ -4,6 +4,13 @@ document.addEventListener('DOMContentLoaded', () => {
   const testCasesElement = document.getElementById('testcases');
   if (testCasesElement) {
     const testCases = [
+      {
+        dateFrom: new Date(2021, 1, 5, 8, 5, 32),
+        dateTo: null,
+        dateFromOptions: {},
+        dateToOptions: {},
+        toString: 'OdsDateTime.format(new Date(2021, 11, 30, 8, 5, 32))',
+      },
       {
         dateFrom: new Date(2021, 11, 30, 8, 5, 32),
         dateTo: null,
diff --git a/src/general/helpers/date_and_time/date_and_time.js b/src/general/helpers/date_and_time/date_and_time.js
index 3529f4c5f..22f0e0bc8 100644
--- a/src/general/helpers/date_and_time/date_and_time.js
+++ b/src/general/helpers/date_and_time/date_and_time.js
@@ -46,6 +46,7 @@ const OdsDateTime = {
         hourCycle: 'h24',
         calendar: 'gregory',
         timeZone: 'Europe/Oslo',
+
       },
     };
     dateFromOptions.type = 'from';
@@ -61,14 +62,14 @@ const OdsDateTime = {
           options.localeOptions = { hour: 'numeric', minute: 'numeric', ...options.localeOptions };
 
           if (options.type === 'to' && typeof options.prefix === 'undefined') {
-            options.prefix = '&mdash;';
+            options.prefix = '–';
           }
           break;
         case 'datetime':
-          options.localeOptions = { year: 'numeric', month: 'numeric', day: 'numeric', hour: 'numeric', minute: 'numeric', ...options.localeOptions };
+          options.localeOptions = { year: 'numeric', month: '2-digit', day: '2-digit', hour: 'numeric', minute: 'numeric', ...options.localeOptions };
 
           if (options.type === 'to' && options.format === 'time' && typeof options.prefix === 'undefined') {
-            options.prefix = '&mdash;';
+            options.prefix = '–';
           }
           break;
         case 'daytime':
@@ -78,10 +79,10 @@ const OdsDateTime = {
           options.localeOptions = { ...options.localeOptions };
           break;
         default:
-          options.localeOptions = { year: 'numeric', month: 'numeric', day: 'numeric', ...options.localeOptions };
+          options.localeOptions = { year: 'numeric', month: '2-digit', day: '2-digit', ...options.localeOptions };
 
           if (options.type === 'to' && typeof options.prefix === 'undefined') {
-            options.prefix = '&mdash;';
+            options.prefix = '–';
           }
       }
     });