diff --git a/cmd/campaigns.go b/cmd/campaigns.go
index 587b109..468105d 100644
--- a/cmd/campaigns.go
+++ b/cmd/campaigns.go
@@ -55,7 +55,7 @@ func addCampaignFieldFlags(cmd *cobra.Command) {
 	cmd.Flags().String("audience-segment-id", "", `Audience segment ID to target. Pass "null" to clear.`)
 	cmd.Flags().String("audience-filter-file", "", `Path to a JSON file with an ad-hoc audience filter. Pass "null" to clear.`)
 	cmd.Flags().Bool("schedule-now", false, "Send immediately when published")
-	cmd.Flags().String("schedule-at", "", "Send at the given RFC3339 timestamp (e.g. 2026-07-01T12:00:00Z)")
+	cmd.Flags().String("schedule-at", "", "Send at the given ISO 8601 timestamp (e.g. 2026-07-01T12:00:00Z)")
 	cmd.MarkFlagsMutuallyExclusive("audience-segment-id", "audience-filter-file")
 	cmd.MarkFlagsMutuallyExclusive("schedule-now", "schedule-at")
 }