Yes. There is one on Mastodon that you can use on Lemmy thanks to federation.
Let’s see if it still works
@remindme@mstdn.social 1 hour
@squirrel Ok, I will remind you on Monday Feb 24, 2025 at 8:58 AM UTC.
This is cool, you can even request the reminder to be sent to your DM! (Add “dm” between remindbots name-pinging and time)
Yes. It’s explained in the bots’ bio
Use me to send you reminders about toots! E.g., “@remindme 1 day”, “@remindme 1 week”, or “@remindme 12h”
You can also use ISO-8601 date times! E.g., “@remindme 2025-03-15”, “@remindme 2025-04-20T12:53-02:00”
If you’d like the reminders to be sent via dm (instead of publicly), add “dm” or “DM” to the message. For example, “@remindme dm 1 day”