diff --git a/fixtures/static/js/json-schema-editor.mjs b/fixtures/static/js/json-schema-editor.mjs
index 341d3dbc..edb2485f 100644
--- a/fixtures/static/js/json-schema-editor.mjs
+++ b/fixtures/static/js/json-schema-editor.mjs
@@ -100,6 +100,7 @@ export class JsonSchemaEditor {
     const value = JSON.parse(this.$module.value);
 
     const data = jsonSchema.getTemplate(value);
+    this.nullEmptyDates(data);
     this.$module.value = JSON.stringify(data);
 
     this.$formContainer.innerHTML = "";
@@ -112,6 +113,19 @@ export class JsonSchemaEditor {
     });
   }
 
+  nullEmptyDates(data) {
+    [
+      "/signedAt",
+      "/witnessedByCertificateProviderAt",
+      "/witnessedByIndependentWitnessAt",
+      "/certificateProviderNotRelatedConfirmedAt",
+    ].forEach((datePointer) => {
+      if (jsonGet(data, datePointer) === "") {
+        jsonSet(data, datePointer, null);
+      }
+    });
+  }
+
   addToArray(pointer) {
     const value = JSON.parse(this.$module.value);
     const arr = jsonGet(value, pointer) ?? [];