diff --git a/database.db b/database.db
index 5e4106e..d82e70b 100644
Binary files a/database.db and b/database.db differ
diff --git a/database.go b/database.go
index b7863cc..31f9b20 100644
--- a/database.go
+++ b/database.go
@@ -14,10 +14,11 @@ import (
 var db *sql.DB
 
 type User struct {
-	UserID   int
-	Username string
-	Passwd   string
-	Type     string
+	UserID    int
+	Username  string
+	Passwd    string
+	Type      string
+	CreatedAt string
 }
 
 func InitDatabase(dbPath string) error {
@@ -85,7 +86,7 @@ func AddUser(username, passwd, userType string) (int, error) { // New user regis
 	return int(lastID), nil
 }
 
-func RemoveUser (userID int) error {
+func RemoveUser(userID int) error {
 	if !isValidInput(strconv.Itoa(userID)) {
 		return errors.New("invalid input: contains illegal characters")
 	}
@@ -113,8 +114,8 @@ func GetUserByUsername(username string) (*User, error) {
 	}
 
 	var user User
-	err := db.QueryRow("SELECT userID, username, passwd, type FROM userLogin WHERE username = ?", username).
-		Scan(&user.UserID, &user.Username, &user.Passwd, &user.Type)
+	err := db.QueryRow("SELECT userID, username, passwd, type, createdAt FROM userLogin WHERE username = ?", username).
+		Scan(&user.UserID, &user.Username, &user.Passwd, &user.Type, &user.CreatedAt)
 	if err != nil {
 		if errors.Is(err, sql.ErrNoRows) {
 			return nil, errors.New("user not found")
@@ -127,8 +128,8 @@ func GetUserByUsername(username string) (*User, error) {
 
 func GetUserByID(userID int) (*User, error) {
 	var user User
-	err := db.QueryRow("SELECT userID, username, passwd, type FROM userLogin WHERE userID = ?", userID).
-		Scan(&user.UserID, &user.Username, &user.Passwd, &user.Type)
+	err := db.QueryRow("SELECT userID, username, passwd, type, createdAt FROM userLogin WHERE userID = ?", userID).
+		Scan(&user.UserID, &user.Username, &user.Passwd, &user.Type, &user.CreatedAt)
 	if err != nil {
 		if errors.Is(err, sql.ErrNoRows) {
 			return nil, errors.New("user not found")
@@ -280,7 +281,8 @@ func InitUserDatabase(dbPath string) error {
 			userID INTEGER PRIMARY KEY AUTOINCREMENT,
 			username TEXT UNIQUE NOT NULL,
 			passwd TEXT NOT NULL,
-			type TEXT NOT NULL DEFAULT 'visitor'
+			type TEXT NOT NULL DEFAULT 'visitor',
+			createdAt TEXT NOT NULL DEFAULT (datetime('now'))
 		);
 		`
 	_, err = db.Exec(createTableSQL)
@@ -292,7 +294,7 @@ func InitUserDatabase(dbPath string) error {
 }
 
 func DBQueryUsers() ([]User, error) { // List all users
-	rows, err := db.Query("SELECT userID, username, type FROM userLogin")
+	rows, err := db.Query("SELECT userID, username, type, createdAt FROM userLogin")
 	if err != nil {
 		return nil, fmt.Errorf("failed to query users: %w", err)
 	}
@@ -300,7 +302,7 @@ func DBQueryUsers() ([]User, error) { // List all users
 	var users []User
 	for rows.Next() {
 		var user User
-		if err := rows.Scan(&user.UserID, &user.Username, &user.Type); err != nil {
+		if err := rows.Scan(&user.UserID, &user.Username, &user.Type, &user.CreatedAt); err != nil {
 			return nil, fmt.Errorf("failed to scan user: %w", err)
 		}
 		users = append(users, user)
@@ -315,7 +317,7 @@ func DBQueryUsers() ([]User, error) { // List all users
 
 func DBQuerySpecificUser(userID int) (User, error) { // Query user by ID
 	var user User
-	err := db.QueryRow("SELECT userID, username, type FROM userLogin WHERE userID = ?", userID).Scan(&user.UserID, &user.Username, &user.Type)
+	err := db.QueryRow("SELECT userID, username, type, createdAt FROM userLogin WHERE userID = ?", userID).Scan(&user.UserID, &user.Username, &user.Type, &user.CreatedAt)
 	if err != nil {
 		return user, fmt.Errorf("failed to query user: %w", err)
 	}
diff --git a/docs/api.md b/docs/api.md
index 2fd537b..132c605 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -299,17 +299,26 @@ X-Timestamp: 1704067200000
     {
       "userID": 1,
       "username": "admin",
-      "type": "superuser"
+      "type": "superuser",
+      "createdAt": "2024-01-01 12:00:00"
     },
     {
       "userID": 2,
       "username": "new_user",
-      "type": "admin"
+      "type": "admin",
+      "createdAt": "2024-01-02 14:30:00"
     }
   ]
 }
 ```
 
+| Field | Type | Description |
+|-------|------|-------------|
+| userID | int | User ID |
+| username | string | Username |
+| type | string | User type: superuser, admin, visitor |
+| createdAt | string | User creation time (YYYY-MM-DD HH:MM:SS format) |
+
 ---
 
 ## List Active Sessions
diff --git a/main.go b/main.go
index 0740e44..8a9052a 100644
--- a/main.go
+++ b/main.go
@@ -89,10 +89,10 @@ func main() {
 
 	go func() {
 		postLog.Info(fmt.Sprintf("Server starting on %s", addr))
+		isOnline = true
 		if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
 			postLog.Fatal(fmt.Sprintf("Failed to start server: %v", err))
 		}
-		isOnline = true
 	}()
 
 	go func() {