统一时间格式和时区

backend/internal/service/callback.go

@@ -17,6 +17,7 @@ import (
 	"time"
 
 	"affiliate_dash/internal/model"
+	"affiliate_dash/internal/pkg/timeutil"
 
 	"github.com/google/uuid"
 	"gorm.io/gorm"
@@ -140,7 +141,7 @@ func (s *CallbackService) Enqueue(tx *gorm.DB, merchantID uint, event string, da
 		payload, err := json.Marshal(map[string]interface{}{
 			"event_id":    eventID,
 			"event":       event,
-			"occurred_at": now.UTC().Format(time.RFC3339Nano),
+			"occurred_at": timeutil.FormatAPITime(now),
 			"data":        data,
 		})
 		if err != nil {