diff --git a/c3l_membership/forms.py b/c3l_membership/forms.py
--- a/c3l_membership/forms.py
+++ b/c3l_membership/forms.py
@@ -57,6 +57,8 @@ class MembershipForm(Form):
         ],
     )
 
+    birthday = DateField("Birthday")
+
     street = StringField(
         "Nr., Street",
         validators=[Length(max=4000)],
diff --git a/c3l_membership/templates/index.html b/c3l_membership/templates/index.html
--- a/c3l_membership/templates/index.html
+++ b/c3l_membership/templates/index.html
@@ -104,6 +104,12 @@
         <legend>Additional information</legend>
         <div class="pure-g">
           <div class="pure-u-1-1">
+            <b>{{ form.birthday.label }}</b>
+            {{ form.birthday(class="pure-u-1-1") }}
+          </div>
+        </div>
+        <div class="pure-g">
+          <div class="pure-u-1-1">
             <b>{{ form.street.label }}</b>
             {{ form.street(class="pure-u-1-1") }}
           </div>
diff --git a/c3l_membership/templates/member.html b/c3l_membership/templates/member.html
--- a/c3l_membership/templates/member.html
+++ b/c3l_membership/templates/member.html
@@ -14,6 +14,8 @@
       <dd>{{ form.email.data }}</dd>
       <dt>Full Name:</dt>
       <dd>{{ form.fullname.data }}</dd>
+      <dt>Birthday:</dt>
+      <dd>{{ form.birthday.data }}</dd>
       <dt>Street:</dt>
       <dd>{{ form.street.data if form.street.data else "<i>Not specified</i>"|safe }}</dd>
       <dt>ZIP-Code:</dt>