I want to get reminders on specific dates.
The web app must be FLOSS and I want to self-host it on my own server (GNU/Linux).
Adding a reminder should be hassle-free and quick. Ideally it only shows a date and a title/description field.
Each reminder must be sent either via SMTP (e-mail) or via XMPP (Jabber). One message per reminder.
Each message should contain a confirmation link. Unless I visit this specific URL, the reminder should be sent again (in configurable intervals).
I don’t necessarily look for a full calendar application; in fact, I’d prefer a smaller, specialized tool. But if a calendar fulfils all requirements, it’s certainly acceptable.