Hi there,
Hope you are doing fine. Google App Engine provides a Cron service. Using this service for scheduling and Google Cloud Pub/Sub for distributed messaging, we can build an application to reliably schedule tasks which can trigger Google Cloud Functions. Using these functions, we can send notification or whatever job required.
We can talk in further detail about the requirements and the specific application. If you have any questions, feel free to ask me. I hope to hear from you soon.