diff --git a/frontend/src/components/TimeSyncNotice.tsx b/frontend/src/components/TimeSyncNotice.tsx
index 67a75e3..9a8e8ff 100644
--- a/frontend/src/components/TimeSyncNotice.tsx
+++ b/frontend/src/components/TimeSyncNotice.tsx
@@ -8,17 +8,15 @@ function formatMs(ms: number) {
 
 export default function TimeSyncNotice({
     thresholdMs = 500,
-    endpoint,
     intervalMs,
     lang = "ja",
 }: {
     thresholdMs?: number;
-    endpoint?: string;
     intervalMs?: number;
     lang?: "ja" | "en";
 }) {
     // removed `error`
-    const { skewMs, rttMs, recheck } = useTimeSkew({ endpoint, intervalMs });
+    const { skewMs, rttMs, recheck } = useTimeSkew({ intervalMs });
 
     const [dismissed, setDismissed] = useState<boolean>(() => {
         try { return sessionStorage.getItem("timesync.dismissed") === "1"; } catch { return false; }
diff --git a/frontend/src/hooks/useTimeSkew.ts b/frontend/src/hooks/useTimeSkew.ts
index 60ca0e9..03d816a 100644
--- a/frontend/src/hooks/useTimeSkew.ts
+++ b/frontend/src/hooks/useTimeSkew.ts
@@ -1,4 +1,5 @@
 import { useEffect, useRef, useState } from "react";
+import { API_ENDPOINT } from "../api/endpoint";
 
 /**
  * Measures client clock skew vs server time {now: <ms since epoch, UTC>}.
@@ -9,6 +10,8 @@ import { useEffect, useRef, useState } from "react";
  *   offset ≈ ((t0 + t1)/2) - s
  * Positive offset => client is AHEAD by that many ms.
  */
+const TIME_URL_ENDPOINT = API_ENDPOINT.v1.TIME;
+
 export function useTimeSkew(opts?: {
     endpoint?: string;     // e.g., "/api/time" or `${import.meta.env.BASE_URL}api/time`
     intervalMs?: number;   // how often to recheck; default 5 min
@@ -16,7 +19,6 @@ export function useTimeSkew(opts?: {
     enabled?: boolean;     // allow turning off; default true
 }) {
     const {
-        endpoint = "/api/time",
         intervalMs = 5 * 60_000,
         samples = 1,
         enabled = true,
@@ -29,7 +31,7 @@ export function useTimeSkew(opts?: {
 
     const measureOnce = async () => {
         const t0 = Date.now();
-        const res = await fetch(endpoint, { cache: "no-store" });
+        const res = await fetch(TIME_URL_ENDPOINT, { cache: "no-store" });
         const t1 = Date.now();
         if (!res.ok) throw new Error(`HTTP ${res.status}`);
         const data = await res.json();
@@ -81,7 +83,7 @@ export function useTimeSkew(opts?: {
             if (timerRef.current) window.clearInterval(timerRef.current);
         };
         // eslint-disable-next-line react-hooks/exhaustive-deps
-    }, [endpoint, intervalMs, samples, enabled]);
+    }, [intervalMs, samples, enabled]);
 
     return { skewMs, rttMs, error, recheck: measure };
 }
\ No newline at end of file