Fix timezone issue in cluster client uptime calculation

- Store connected_at as proper UTC timestamp in database using FROM_UNIXTIME/datetime
- Update web interface to handle datetime objects and timestamps correctly
- Ensure uptime starts from actual connection time, not offset by timezone

vidai/database.py

@@ -1656,15 +1656,14 @@ def save_cluster_client(client_id: str, token: str, hostname: str, ip_address: s
     if connected_at is None:
         connected_at = time.time()
 
-    # Convert to datetime string for database storage
-    from datetime import datetime
-    connected_at_str = datetime.utcfromtimestamp(connected_at).strftime('%Y-%m-%d %H:%M:%S')
+    # Store as Unix timestamp (float) to avoid timezone issues
+    connected_at_value = connected_at
 
     config = get_db_config()
     if config['type'] == 'mysql':
         cursor.execute('''
             INSERT INTO cluster_clients (client_id, token, hostname, ip_address, weight, gpu_info, available_backends, connected, connected_at, last_seen)
-            VALUES (?, ?, ?, ?, ?, ?, ?, 1, ?, CURRENT_TIMESTAMP)
+            VALUES (?, ?, ?, ?, ?, ?, ?, 1, FROM_UNIXTIME(?), CURRENT_TIMESTAMP)
             ON DUPLICATE KEY UPDATE
                 hostname = VALUES(hostname),
                 ip_address = VALUES(ip_address),
@@ -1672,16 +1671,16 @@ def save_cluster_client(client_id: str, token: str, hostname: str, ip_address: s
                 gpu_info = VALUES(gpu_info),
                 available_backends = VALUES(available_backends),
                 connected = 1,
-                connected_at = VALUES(connected_at),
+                connected_at = FROM_UNIXTIME(?),
                 last_seen = CURRENT_TIMESTAMP
-        ''', (client_id, token, hostname, ip_address, weight, gpu_info_json, available_backends_json, connected_at_str))
+        ''', (client_id, token, hostname, ip_address, weight, gpu_info_json, available_backends_json, connected_at_value, connected_at_value))
     else:
         # For SQLite
         cursor.execute('''
             INSERT OR REPLACE INTO cluster_clients
             (client_id, token, hostname, ip_address, weight, gpu_info, available_backends, connected, connected_at, last_seen)
-            VALUES (?, ?, ?, ?, ?, ?, ?, 1, ?, CURRENT_TIMESTAMP)
-        ''', (client_id, token, hostname, ip_address, weight, gpu_info_json, available_backends_json, connected_at_str))
+            VALUES (?, ?, ?, ?, ?, ?, ?, 1, datetime(?, 'unixepoch'), CURRENT_TIMESTAMP)
+        ''', (client_id, token, hostname, ip_address, weight, gpu_info_json, available_backends_json, connected_at_value))
 
     conn.commit()
     success = cursor.rowcount > 0

vidai/web.py

@@ -447,6 +447,10 @@ def api_cluster_nodes():
                     # Parse timestamp string
                     import datetime
                     connected_at = datetime.datetime.fromisoformat(connected_at.replace('Z', '+00:00')).timestamp()
+                elif hasattr(connected_at, 'timestamp'):
+                    # datetime object
+                    connected_at = connected_at.timestamp()
+                # If it's already a float/int timestamp, use it directly
                 uptime_seconds = current_time - connected_at
             else:
                 uptime_seconds = 0