diff --git a/components/cli/command/service/logs.go b/components/cli/command/service/logs.go
index 19d3d9a488..40e7bd41fd 100644
--- a/components/cli/command/service/logs.go
+++ b/components/cli/command/service/logs.go
@@ -45,7 +45,7 @@ func newLogsCommand(dockerCli *command.DockerCli) *cobra.Command {
 	flags := cmd.Flags()
 	flags.BoolVar(&opts.noResolve, "no-resolve", false, "Do not map IDs to Names")
 	flags.BoolVarP(&opts.follow, "follow", "f", false, "Follow log output")
-	flags.StringVar(&opts.since, "since", "", "Show logs since timestamp")
+	flags.StringVar(&opts.since, "since", "", "Show logs since timestamp (e.g. 2013-01-02T13:23:37) or relative (e.g. 42m for 42 minutes)")
 	flags.BoolVarP(&opts.timestamps, "timestamps", "t", false, "Show timestamps")
 	flags.BoolVar(&opts.details, "details", false, "Show extra details provided to logs")
 	flags.StringVar(&opts.tail, "tail", "all", "Number of lines to show from the end of the logs")