diff --git a/docs/en/modules/cron.md b/docs/en/modules/cron.md
index baaa22ac..2838c511 100644
--- a/docs/en/modules/cron.md
+++ b/docs/en/modules/cron.md
@@ -7,6 +7,9 @@
 
 !!! important
     This module needs RTC time to operate correctly. Do not forget to include the [`rtctime`](rtctime.md) module **and** initialize it properly.
+    
+!!! important
+    The cron expression has to be in GMT/UTC!
 
 ## cron.schedule()