Rest Your Eyes - Prevent eyestrain caused by screens with the 20-20 rule.
Cron - Cron Calendar.
Eye Yoga - Improve eyesight, relieve eye strain and prevent presbyopia.
zcal - zcal is the fastest way to schedule every meeting for Free and make it personal.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.