diff --git a/cli/command/container/logs.go b/cli/command/container/logs.go
index d9bc73baff..8dabbfad6b 100644
--- a/cli/command/container/logs.go
+++ b/cli/command/container/logs.go
@@ -38,8 +38,8 @@ func NewLogsCommand(dockerCli command.Cli) *cobra.Command {
 
 	flags := cmd.Flags()
 	flags.BoolVarP(&opts.follow, "follow", "f", false, "Follow log output")
-	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.StringVar(&opts.until, "until", "", "Show logs before a timestamp (e.g. 2013-01-02T13:23:37) or relative (e.g. 42m for 42 minutes)")
+	flags.StringVar(&opts.since, "since", "", "Show logs since timestamp (e.g. 2013-01-02T13:23:37Z) or relative (e.g. 42m for 42 minutes)")
+	flags.StringVar(&opts.until, "until", "", "Show logs before a timestamp (e.g. 2013-01-02T13:23:37Z) or relative (e.g. 42m for 42 minutes)")
 	flags.SetAnnotation("until", "version", []string{"1.35"})
 	flags.BoolVarP(&opts.timestamps, "timestamps", "t", false, "Show timestamps")
 	flags.BoolVar(&opts.details, "details", false, "Show extra details provided to logs")
diff --git a/cli/command/service/logs.go b/cli/command/service/logs.go
index 107c9d2153..deef9dd221 100644
--- a/cli/command/service/logs.go
+++ b/cli/command/service/logs.go
@@ -59,7 +59,7 @@ func newLogsCommand(dockerCli command.Cli) *cobra.Command {
 	flags.BoolVar(&opts.noTaskIDs, "no-task-ids", false, "Do not include task IDs in output")
 	// options identical to container logs
 	flags.BoolVarP(&opts.follow, "follow", "f", false, "Follow log output")
-	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.StringVar(&opts.since, "since", "", "Show logs since timestamp (e.g. 2013-01-02T13:23:37Z) 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.SetAnnotation("details", "version", []string{"1.30"})
diff --git a/docs/reference/commandline/logs.md b/docs/reference/commandline/logs.md
index 76502989e1..36e21f1361 100644
--- a/docs/reference/commandline/logs.md
+++ b/docs/reference/commandline/logs.md
@@ -15,8 +15,8 @@ Options:
       --details        Show extra details provided to logs
   -f, --follow         Follow log output
       --help           Print usage
-      --since string   Show logs since timestamp (e.g. 2013-01-02T13:23:37) or relative (e.g. 42m for 42 minutes)
-      --until string   Show logs before timestamp (e.g. 2013-01-02T13:23:37) or relative (e.g. 42m for 42 minutes)
+      --since string   Show logs since timestamp (e.g. 2013-01-02T13:23:37Z) or relative (e.g. 42m for 42 minutes)
+      --until string   Show logs before timestamp (e.g. 2013-01-02T13:23:37Z) or relative (e.g. 42m for 42 minutes)
       --tail string    Number of lines to show from the end of the logs (default "all")
   -t, --timestamps     Show timestamps
 ```