diff --git a/service/DiscoveryService.go b/service/DiscoveryService.go
index 4ddf0f4..67d8e54 100644
--- a/service/DiscoveryService.go
+++ b/service/DiscoveryService.go
@@ -2,7 +2,6 @@ package service
 
 import (
 	"reflect"
-	"time"
 
 	cda "git.loafle.net/commons/di-go/annotation"
 	cdr "git.loafle.net/commons/di-go/registry"
@@ -12,6 +11,7 @@ import (
 
 	// For annotation
 	_ "git.loafle.net/overflow/commons-go/core/annotation"
+	"git.loafle.net/overflow/commons-go/core/util"
 )
 
 var DiscoveryServiceType = reflect.TypeOf((*DiscoveryService)(nil))
@@ -63,11 +63,11 @@ func (s *DiscoveryService) DiscoverService(requesterID string, port *ocmd.Port,
 }
 
 // use by discovery
-func (s *DiscoveryService) DiscoveryStart(requesterID string, t *time.Time) error {
+func (s *DiscoveryService) DiscoveryStart(requesterID string, t *util.Timestamp) error {
 	return s.ProbeClientService.Send("DiscoveryService.discoveryStart", requesterID, t)
 }
 
-func (s *DiscoveryService) DiscoveryStop(requesterID string, t *time.Time) error {
+func (s *DiscoveryService) DiscoveryStop(requesterID string, t *util.Timestamp) error {
 	return s.ProbeClientService.Send("DiscoveryService.discoveryStop", requesterID, t)
 }