diff --git a/src/components/Jodetail/PlasticBoxCartonDashboardTab.tsx b/src/components/Jodetail/PlasticBoxCartonDashboardTab.tsx
index e9d9f16..92eef86 100644
--- a/src/components/Jodetail/PlasticBoxCartonDashboardTab.tsx
+++ b/src/components/Jodetail/PlasticBoxCartonDashboardTab.tsx
@@ -28,6 +28,9 @@ import {
 } from "@/app/api/jo/actions";
 import SafeApexCharts from "@/components/charts/SafeApexCharts";
 
+/** Day.js has no typed `dayjs.invalid()` factory; Invalid Date parses to an invalid Dayjs instance. */
+const DAYJS_INVALID = dayjs(new Date(Number.NaN));
+
 type FloorFilter = "all" | "2/F" | "3/F" | "4/F";
 
 type DailySummaryRow = {
@@ -51,14 +54,14 @@ const parseRecordDate = (record: CompletedJobOrderPickOrderDashboardRecord): day
   }
 
   const raw = record.completedDate ?? record.planStart;
-  if (!raw) return dayjs.invalid();
+  if (!raw) return DAYJS_INVALID;
 
   if (Array.isArray(raw)) {
     const [year, month, day] = raw;
     if (year != null && month != null && day != null) {
       return dayjs(new Date(Number(year), Number(month) - 1, Number(day)));
     }
-    return dayjs.invalid();
+    return DAYJS_INVALID;
   }
 
   if (typeof raw === "string") {