Scheduled tasks - GNOME GUI for configuring a users' cron (automatic jobs). Some of its features are:
Reminduck - A simple reminder app made for elementaryOS with Vala and GTK. - matfantinel/reminduck
Digital Clock 4 - Beautiful customizable clock with plugins
Reminder Commander - Reminder manager that reminds you about important events in advance.
Advanced Task Scheduler - A powerful and versatile task scheduler.
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.