Dayweave

Dayweave brings your tasks, deadlines, habits, calendar, focus sessions and
analytics together in one application. All data stays on your computer, with
no account, no cloud service, no telemetry and no network access.

Reminders are delivered while Dayweave is running, including when its window
is closed and it is waiting in the system tray. Quitting stops them until the
next launch. Turn on Start at login in Settings to have them from sign-in.