Your service for a time trigger?

Question

ubuntu

Colleagues, hello.
Already searched everything on the Internet. Please tell me if there is any service for triggering a certain url (a la webhook) at a certain time.
What I want: ideally, find a self-hosted service, in the admin panel of which I create the event "01/12/1990 at 15:00 publish the news "SERVER RESTART"), exactly at this time the service triggers a webhook that leads to domain.com/sendMessage - - this handle will send a message to telegram chat with (either) the content "restarting the server" or with the content "go to the service ... and see the upcoming event".
If such a service is difficult to implement or there are no self-hosted solutions, then maybe there is an alternative? For example, some self-hosted web cron, to which I say "at <this> time, execute the command curl domain.com/sendMessage?message="Rebooting server"
Of course, the first method is preferable and clearer, but I really can't find it yet There was an
idea to use cachet as a service for posting such events, but there are no webhooks there,
or statping - you can create a mailing list and use webhooks there... But, IMHO, this is a crutch
.
Thank you
(highly preferable if the service is self-hosted )