Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
Google Calendar - Spend less time managing your day & more time enjoying it
wnr - Better than pomodoro, this timer app balances work and rest.
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.
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows