There are times when you want to remind your future self about something. Most people remind themselves about things in the future - pending tasks or events bound to happen. I personally like to remind my future self of current events too - like, what happened yesterday.
Regardless of your need, adding a reminder is built-in in Logseq and extremely easy to add (though a bit hidden from the public):
When the time is due, those will appear within the journal for the given day. You can even make those reminders appear on multiple days.
The only downside is that those reminders remain in Logseq. As far as I know, there is no built-in way to send notifications outside the application. Of course, there is a comprehensive ecosystem of 3rd-party extensions developed by the community. I am sure multiple ones could do this for you. If you know about a good one, don’t hesitate to add a comment below.