diff --git a/web/static/booking-dates.js b/web/static/booking-dates.js
index 4df951a..43bbc84 100644
--- a/web/static/booking-dates.js
+++ b/web/static/booking-dates.js
@@ -3,7 +3,7 @@
 
     function updateDepartureDate(arrivalDateField) {
         const arrivalDate = new Date(arrivalDateField.value);
-        if (isNaN(arrivalDate)) {
+        if (isNaN(arrivalDate.getTime())) {
             return;
         }
         const departureDateField = document.querySelector('[name="departure_date"]');
@@ -17,7 +17,8 @@
 
         departureDateField.setAttribute('min', minDate);
         const departureDate = new Date(departureDateField.value);
-        if (isNaN(departureDate) || departureDate < arrivalDate) {
+        const validDepartureDate = !isNaN(departureDate.getTime())
+        if (!validDepartureDate || departureDate < arrivalDate) {
             departureDateField.value = minDate;
         }
 
@@ -26,7 +27,7 @@
             arrivalDate.setUTCDate(arrivalDate.getUTCDate() + maxNights - minNights);
             const maxDate = formatDate(arrivalDate);
             departureDateField.setAttribute('max', maxDate);
-            if (!isNaN(departureDate) && departureDate >= arrivalDate) {
+            if (validDepartureDate && departureDate >= arrivalDate) {
                 departureDateField.value = maxDate;
             }
         }