Desktop-Reminder - Desktop-Reminder is a freeware task planner for Windows to manage your tasks and other to-dos’ in really easy way.
Crontab UI - Easy and safe way to manage your crontab file
Reminduck - A simple reminder app made for elementaryOS with Vala and GTK. - matfantinel/reminduck
Scheduled tasks - GNOME GUI for configuring a users' cron (automatic jobs). Some of its features are:
024h Lucky Reminder - 024h Lucky Reminder is a reminder software for home and office.
Holiline Reminder - Holiline Reminder is both an event reminder and a calendar.