diff --git a/src/pretix/base/reldate.py b/src/pretix/base/reldate.py
index 1f609bc1d0..b16cb7907b 100644
--- a/src/pretix/base/reldate.py
+++ b/src/pretix/base/reldate.py
@@ -21,7 +21,7 @@
 #
 import datetime
 from collections import namedtuple
-from typing import Union
+from typing import Tuple, Union
 from zoneinfo import ZoneInfo
 
 from dateutil import parser
@@ -42,6 +42,7 @@ EVENT_CHOICES = (
     ('presale_end', _('Presale end')),
 )
 
+# extend NO_BEFORE_VALUES in reldate.js if changed
 ORDER_CHOICES = (
     ('datetime', _('Moment of order')),
 )
diff --git a/src/pretix/base/templates/pretixbase/forms/widgets/reldate.html b/src/pretix/base/templates/pretixbase/forms/widgets/reldate.html
index 73b8ff7c3d..b3113e2584 100644
--- a/src/pretix/base/templates/pretixbase/forms/widgets/reldate.html
+++ b/src/pretix/base/templates/pretixbase/forms/widgets/reldate.html
@@ -1,4 +1,6 @@
 {% load i18n %}
+{% load static %}
+<script src="{% static 'pretixbase/js/reldate.js' %}" defer></script>
 <div class="reldatetime">
     {% for group_name, group_choices, group-index in widget.subwidgets.0.optgroups %}
         {% for selopt in group_choices %}
diff --git a/src/pretix/base/templates/pretixbase/forms/widgets/reldatetime.html b/src/pretix/base/templates/pretixbase/forms/widgets/reldatetime.html
index 3e618d0910..31acdf0614 100644
--- a/src/pretix/base/templates/pretixbase/forms/widgets/reldatetime.html
+++ b/src/pretix/base/templates/pretixbase/forms/widgets/reldatetime.html
@@ -1,4 +1,6 @@
 {% load i18n %}
+{% load static %}
+<script src="{% static 'pretixbase/js/reldate.js' %}" defer></script>
 <div class="reldatetime">
     {% for group_name, group_choices, group-index in widget.subwidgets.0.optgroups %}
         {% for selopt in group_choices %}
diff --git a/src/pretix/static/pretixbase/js/reldate.js b/src/pretix/static/pretixbase/js/reldate.js
new file mode 100644
index 0000000000..9539a50f86
--- /dev/null
+++ b/src/pretix/static/pretixbase/js/reldate.js
@@ -0,0 +1,44 @@
+if (!window.__reldateInitialized) {
+    window.__reldateInitialized = true;
+    document.addEventListener('DOMContentLoaded', () => {
+         const NO_BEFORE_VALUES = ['datetime'];
+
+        document.querySelectorAll('.reldatetime, .reldate').forEach(container => {
+            const groups = container.querySelectorAll('.radio');
+
+            groups.forEach(group => {
+                const selects = group.querySelectorAll('select');
+                if (selects.length < 2) return;
+
+                let referenceSelect = null;
+                let beforeAfterSelect = null;
+
+                selects.forEach(sel => {
+                    const values = Array.from(sel.options).map(o => o.value);
+                    // only attach to selects that contain problematic values
+                    if (NO_BEFORE_VALUES.some(v => values.includes(v))) {
+                        referenceSelect = sel;
+                    } else if (values.includes('before') && values.includes('after')) {
+                        beforeAfterSelect = sel;
+                    }
+                });
+                if (!referenceSelect || !beforeAfterSelect) return;
+
+                const beforeOption = beforeAfterSelect.querySelector('option[value="before"]');
+                const updateBeforeOption = () => {
+                    if (NO_BEFORE_VALUES.includes(referenceSelect.value)) {
+                        beforeOption.disabled = true;
+                        if (beforeAfterSelect.value === 'before') {
+                            beforeAfterSelect.value = 'after';
+                            beforeAfterSelect.dispatchEvent(new Event('change', { bubbles: true }));
+                        }
+                    } else {
+                        beforeOption.disabled = false;
+                    }
+                };
+                referenceSelect.addEventListener('change', updateBeforeOption);
+                updateBeforeOption();
+            });
+        });
+    });
+}