diff --git wp-includes/cron.php wp-includes/cron.php
index 8b88c12..5f4946e 100644
--- wp-includes/cron.php
+++ wp-includes/cron.php
@@ -21,6 +21,11 @@
  * @return void|false
  */
 function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
+	// check timestamp positive number
+	if ( ! is_numeric( $timestamp ) || $timestamp <= 0 ){
+		return ;
+	}
+
 	// don't schedule a duplicate if there's already an identical event due within 10 minutes of it
 	$next = wp_next_scheduled($hook, $args);
 	if ( $next && abs( $next - $timestamp ) <= 10 * MINUTE_IN_SECONDS ) {