Update action.yml

.github/workflows/action.yml

@@ -3,9 +3,9 @@ name: NIMBLE
 # Controls when the action will run. Triggers the workflow on push or pull request
 # events but only for the master branch
 on:
-  # Runs at 16:00 UTC (BeiJing 00:00) on the 30st of every month
+  # Runs at 16:00 UTC (BeiJing 00:00) on the 31st of March
   schedule:
-    - cron:  '0 9 31 * *'
+    - cron:  '0 9 31 3,9 *'
   push:
     branches:
       - master