Fix timestamps

commonspace/object/tree/objecttree/change.go

@@ -53,6 +53,7 @@ func NewChangeFromRoot(id string, ch *treechangeproto.RootChange, signature []by
 		AclHeadId:  ch.AclHeadId,
 		Id:         id,
 		IsSnapshot: true,
+		Timestamp:  ch.Timestamp,
 		Identity:   string(ch.Identity),
 		Signature:  signature,
 		Data:       []byte(ch.ChangeType),

commonspace/object/tree/objecttree/changebuilder.go

@@ -151,7 +151,7 @@ func (c *changeBuilder) BuildContent(payload BuilderContent) (ch *Change, rawIdC
 		AclHeadId:          payload.AclHeadId,
 		SnapshotBaseId:     payload.SnapshotBaseId,
 		CurrentReadKeyHash: payload.CurrentReadKeyHash,
-		Timestamp:          int64(time.Now().Nanosecond()),
+		Timestamp:          time.Now().UnixNano(),
 		Identity:           payload.Identity,
 		IsSnapshot:         payload.IsSnapshot,
 	}