Replace menu bar clock with a drop-down calendar.
FromShaun Inman:Day-O is a simple menu bar clock replacement with a simple calendar for your Mac. It's free, as-is (which means I'm not providing support, taking feature requests, addressing perceived inadequacies or releasing the source code).
Darkens the desktop & icons to help you focus.
Monitor and update your current time based on selected time zones.
Simple countdown timer app with a visual readout.