Google Calendar - Spend less time managing your day & more time enjoying it
Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
Lightning Calendar - Organize your life — it’s about time!
SnapTimer - SnapTimer is a simple, free, portable countdown timer for Windows.
Morgen.so - All-in-one Calendar, Tasks & Scheduler. Morgen is the single hub for everything that revolves around time management.
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows