diff --git a/backend/database.js b/backend/database.js
index 6667532..10c88b0 100644
--- a/backend/database.js
+++ b/backend/database.js
@@ -303,7 +303,9 @@ const ShareDB = {
     if (expiry_days) {
       const expireDate = new Date();
       expireDate.setDate(expireDate.getDate() + parseInt(expiry_days));
-      expiresAt = expireDate.toISOString();
+      // 转换为SQLite datetime格式 (YYYY-MM-DD HH:MM:SS),而不是ISO格式
+      // 这样才能正确与 datetime('now') 进行比较
+      expiresAt = expireDate.toISOString().replace('T', ' ').replace(/\.\d+Z$/, '');
     }
 
     const stmt = db.prepare(`
diff --git a/backend/fix_expires_at_format.js b/backend/fix_expires_at_format.js
new file mode 100644
index 0000000..c039db7
--- /dev/null
+++ b/backend/fix_expires_at_format.js
@@ -0,0 +1,34 @@
+const { db } = require('./database');
+
+console.log('开始修复 expires_at 格式...\n');
+
+// 查找所有有过期时间的分享
+const shares = db.prepare(`
+  SELECT id, share_code, expires_at
+  FROM shares
+  WHERE expires_at IS NOT NULL
+`).all();
+
+console.log(`找到 ${shares.length} 条需要修复的记录\n`);
+
+let fixed = 0;
+const updateStmt = db.prepare('UPDATE shares SET expires_at = ? WHERE id = ?');
+
+shares.forEach(share => {
+  const oldFormat = share.expires_at;
+  
+  // 如果是ISO格式(包含T和Z),需要转换
+  if (oldFormat.includes('T') || oldFormat.includes('Z')) {
+    // 转换为 SQLite datetime 格式: YYYY-MM-DD HH:MM:SS
+    const newFormat = oldFormat.replace('T', ' ').replace(/\.\d+Z$/, '');
+    
+    updateStmt.run(newFormat, share.id);
+    fixed++;
+    
+    console.log(`✓ 修复分享 ${share.share_code}:`);
+    console.log(`  旧格式: ${oldFormat}`);
+    console.log(`  新格式: ${newFormat}\n`);
+  }
+});
+
+console.log(`\n修复完成! 共修复 ${fixed} 条记录`);