diff --git a/web/src/components/UsageHeatMap.tsx b/web/src/components/UsageHeatMap.tsx
index da9ef231..fe659d07 100644
--- a/web/src/components/UsageHeatMap.tsx
+++ b/web/src/components/UsageHeatMap.tsx
@@ -47,7 +47,7 @@ const UsageHeatMap: React.FC<Props> = () => {
   useEffect(() => {
     const newStat: DailyUsageStat[] = getInitialUsageStat(usedDaysAmount, beginDayTimestemp);
     for (const m of memos) {
-      const index = (utils.getDateStampByDate(m.createdAt) - beginDayTimestemp) / (1000 * 3600 * 24) - 1;
+      const index = (utils.getDateStampByDate(m.createdTs) - beginDayTimestemp) / (1000 * 3600 * 24) - 1;
       if (index >= 0) {
         newStat[index].count += 1;
       }