Cron - Cron Calendar.
Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
zcal - zcal is the fastest way to schedule every meeting for Free and make it personal.
myPoli - Gameified to-do list and habit tracker.
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.
ATracker - ATracker app allows you to track your time in a few simple steps and can view full daily, weekly, and monthly reports at a glance.