diff --git a/config/services.yaml b/config/services.yaml
index b803881..370340d 100644
--- a/config/services.yaml
+++ b/config/services.yaml
@@ -72,6 +72,7 @@ services:
         arguments:
             $handlers:
                 # Simple handlers (no dependencies) - use class names
+                - 'App\Form\Service\ParticipantDateOfBirthFieldHandler'
                 - 'App\Form\Service\ParticipantAssignedRoomFieldHandler'
                 # Complex handlers (with dependencies) would use service references like:
                 # - '@participant.complex.handler'
diff --git a/src/Form/Service/ParticipantDateOfBirthFieldHandler.php b/src/Form/Service/ParticipantDateOfBirthFieldHandler.php
new file mode 100644
index 0000000..c1d0541
--- /dev/null
+++ b/src/Form/Service/ParticipantDateOfBirthFieldHandler.php
@@ -0,0 +1,110 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Form\Service;
+
+use App\Form\Model\BookingDtoInterface;
+use App\Form\Service\Abstract\AbstractParticipantFieldHandler;
+
+/**
+ * Handles processing of the dateOfBirth field for booking participants.
+ *
+ * This handler manages date of birth processing for participants in the booking creation
+ * and edit processes. It processes the dateOfBirth field from form submissions and updates
+ * the participant DTO with the provided date. This is crucial for age-based field visibility
+ * and service filtering during HTMX form updates.
+ *
+ * Field Processing:
+ * - Extracts date of birth from submitted form data
+ * - Converts form date strings to DateTimeImmutable objects
+ * - Handles empty selections (converting them to null)
+ * - Updates the participant's dateOfBirth property
+ *
+ * Dependencies: None (this is a base field that other handlers may depend on)
+ */
+class ParticipantDateOfBirthFieldHandler extends AbstractParticipantFieldHandler
+{
+    /**
+     * Returns the form field name this handler processes.
+     *
+     * This handler is responsible for the 'dateOfBirth' field, which contains
+     * the birth date for each participant in the booking form.
+     *
+     * @return string The field name 'dateOfBirth'
+     */
+    public function getFieldName(): string
+    {
+        return 'dateOfBirth';
+    }
+
+    /**
+     * Processes the dateOfBirth field for a specific participant.
+     *
+     * This method extracts the date of birth from the submitted form data and
+     * updates the corresponding participant in the booking DTO. It handles the
+     * conversion from form date strings to DateTimeImmutable objects and properly
+     * handles empty selections.
+     *
+     * Processing steps:
+     * 1. Safely retrieves the participant object from the DTO
+     * 2. Extracts the dateOfBirth value from submitted data
+     * 3. Normalizes the value (empty string → null, date string → DateTimeImmutable)
+     * 4. Updates the participant's dateOfBirth property
+     *
+     * @param array<string, mixed> $submittedData    The submitted participant form data
+     * @param BookingDtoInterface  $bookingDto       The booking DTO to update (create or edit)
+     * @param int                  $participantIndex The index of the participant being processed
+     */
+    public function processField(array $submittedData, BookingDtoInterface $bookingDto, int $participantIndex): void
+    {
+        // Safely get the participant object, returning early if not found
+        $participant = $this->getParticipant($bookingDto, $participantIndex);
+
+        if (null === $participant) {
+            return;
+        }
+
+        // Extract the date of birth from form data (defaults to null if not present)
+        $dateOfBirth = $this->getFieldValue($submittedData, $this->getFieldName());
+
+        // Convert form date to DateTimeImmutable, handling empty selections as null
+        $participant->dateOfBirth = $this->normalizeDateValue($dateOfBirth);
+    }
+
+    /**
+     * Normalizes a date value from form submission to DateTimeImmutable or null.
+     *
+     * This method handles the conversion of form date values to proper DateTimeImmutable
+     * objects. It gracefully handles empty strings, null values, and invalid date formats.
+     *
+     * @param mixed $value The raw value from form submission
+     *
+     * @return \DateTimeImmutable|null The normalized date or null if empty/invalid
+     */
+    private function normalizeDateValue(mixed $value): ?\DateTimeImmutable
+    {
+        // Handle null or empty string (no date selected)
+        if (null === $value || '' === trim((string) $value)) {
+            return null;
+        }
+
+        // If already a DateTimeInterface, convert to DateTimeImmutable
+        if ($value instanceof \DateTimeInterface) {
+            return \DateTimeImmutable::createFromInterface($value);
+        }
+
+        // Try to parse string date
+        if (is_string($value)) {
+            try {
+                return new \DateTimeImmutable($value);
+            } catch (\Exception $e) {
+                // Invalid date format, return null
+                return null;
+            }
+        }
+
+        // Unsupported type, return null
+        return null;
+    }
+}
\ No newline at end of file
diff --git a/templates/booking/create_step_2.html.twig b/templates/booking/create_step_2.html.twig
index e80abbc..3b15a49 100644
--- a/templates/booking/create_step_2.html.twig
+++ b/templates/booking/create_step_2.html.twig
@@ -27,7 +27,13 @@
                                     <div class="grid grid-cols-2 gap-4 pb-4">
                                         {{ form_row(participant.firstName) }}
                                         {{ form_row(participant.lastName) }}
-                                        {{ form_row(participant.dateOfBirth) }}
+                                        {# hx-swap="none" tells HTMX not to do a normal swap, as OOB will handle it #}
+                                        {{ form_row(participant.dateOfBirth, {
+                                            'attr': {
+                                                'hx-post': path('app_booking_create_step_2_refresh'),
+                                                'hx-swap': 'none'
+                                            }
+                                        }) }}
                                         {{ form_row(participant.gender) }}
                                         {{ form_row(participant.nationality) }}
                                     </div>