If you don’t have an Apple computer but have an iOS device, you can also do something similar with the “Shortcuts.app” + “Calendar.app”.
I have a daily shortcut that runs at X time. Shortcut checks a calendar for events, if today contains one or more events. It will parse the text from these events (comma separated fully qualified phone numbers or iMessage accounts), and send the message contained in the body of the event.
Added bonus here is that I can also send group messages.
If I need to have the message sent on repeat, then I put the cal event on repeat.
I could possibly even have templated messages (ie, insert month and year into message), but I haven’t deep dived into that rabbit hole.
Downside here though is that you need an iOS device to always be on.