diff --git a/src/lib/render-date-to-html.ts b/src/lib/render-date-to-html.ts
index 7661b37..6d5a2cc 100644
--- a/src/lib/render-date-to-html.ts
+++ b/src/lib/render-date-to-html.ts
@@ -4,6 +4,7 @@ const locale = `${SITE_LANG}-${SITE_REGION}`;
 
 const dateFormatter = new Intl.DateTimeFormat(locale, {
   dateStyle: 'long',
+  timeZone: 'Asia/Tokyo',
 });
 
 export function renderDateToHtml(date: Date) {
diff --git a/src/lib/render-year-month-range-to-html.ts b/src/lib/render-year-month-range-to-html.ts
index 0005d0f..d215322 100644
--- a/src/lib/render-year-month-range-to-html.ts
+++ b/src/lib/render-year-month-range-to-html.ts
@@ -14,6 +14,7 @@ const locale = `${SITE_LANG}-${SITE_REGION}`;
 const yearMonthFormatter = new Intl.DateTimeFormat(locale, {
   year: 'numeric',
   month: 'long',
+  timeZone: 'Asia/Tokyo',
 });
 
 function renderYearMonthToHtml(yearMonth: YearMonth) {