Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
Timer Tab - Online countdown timer, alarm clock, and stopwatch.
Google Calendar - Spend less time managing your day & more time enjoying it
Online timer - Online timer is a free and easy-to-use tool that comes with a very simple way to get done with measuring time and alarm.
Itsycal - Itsycal for Mac. Itsycal is a tiny menu bar calendar. If you want, it will display your events as a companion to the Mac Calendar app. You can also create and delete (but not edit) events. Download Itsycal for macOS 10.
Online Stopwatch - Online Stopwatch is free to use online tool that allows you to keep track of the important events and tasks that you are performing.