diff --git a/src/components/WindowSizeExample.jsx b/src/components/WindowSizeExample.jsx
index 8a4c768..295affd 100644
--- a/src/components/WindowSizeExample.jsx
+++ b/src/components/WindowSizeExample.jsx
@@ -1,26 +1,9 @@
-import { useEffect, useState } from "react";
+import { useWindowSize } from "../hooks/useWindowSize";
 
 export const WindowSizeExample = () => {
   // 실습 1. 하단 코드를 useWindowSize (커스텀 훅으로 바꿔주세요!)
-  const [windowSize, setWindowSize] = useState({
-    width: window.innerWidth,
-    height: window.innerHeight,
-  });
-
-  useEffect(() => {
-    const handleResize = () => {
-      setWindowSize({
-        width: window.innerWidth,
-        height: window.innerHeight,
-      });
-    };
-
-    window.addEventListener("resize", handleResize);
-
-    return () => {
-      window.removeEventListener("resize", handleResize);
-    };
-  }, []);
+  // const { windowSize } = useWindowSize(); // 훅이 객체를 반환하고, 그 객체 안에 windowSize라는 속성이 있는 경우
+  const windowSize = useWindowSize();  // 이건 useWindowSize()가 windowSize 객체 자체를 반환하는 경우에만 사용
 
   return (
     <div>
@@ -30,3 +13,4 @@ export const WindowSizeExample = () => {
     </div>
   );
 };
+
diff --git a/src/hooks/useCountdown.js b/src/hooks/useCountdown.js
index 19c04c3..4dc3f18 100644
--- a/src/hooks/useCountdown.js
+++ b/src/hooks/useCountdown.js
@@ -1,3 +1,12 @@
+import { useEffect, useState } from "react";
+const targetDate = new Date("2025-08-25T00:00:00");
+
 export const useCountdown = (targetDate) => {
+  const difference = targetDate.getTime() - Date().getTime();
+
+  const Days = Math.floor(difference / (1000*60*60*24));
+
+
+
   return timeLeft;
 };
diff --git a/src/hooks/useWindowSize.js b/src/hooks/useWindowSize.js
index 28d9f7c..2e8c117 100644
--- a/src/hooks/useWindowSize.js
+++ b/src/hooks/useWindowSize.js
@@ -1 +1,27 @@
 // 커스텀훅 코드를 작성해보세요!
+import { useEffect, useState } from "react";
+
+//defalut 여부
+export const useWindowSize = () => {
+  const [windowSize, setWindowSize] = useState({
+    width: window.innerWidth,
+    height: window.innerHeight,
+  });
+
+  useEffect(() => {
+    const handelResize = () => { //setWindowSize를 호출
+      setWindowSize({
+        width: window.innerWidth,
+        height: window.innerHeight,
+      });
+    };
+  
+    window.addEventListener("resize", handelResize);
+
+    return () => {
+      window.removeEventListener("resize", handelResize);
+    };
+  }, []);
+
+  return windowSize;
+};
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