Crontab UI - Easy and safe way to manage your crontab file
Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
Scheduled tasks - GNOME GUI for configuring a users' cron (automatic jobs). Some of its features are:
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
024h Lucky Reminder - 024h Lucky Reminder is a reminder software for home and office.
pretix - pretix helps you to sell tickets for your event in an easy way. It supports multi-lingual events and provides a wide range of features