Top rated in Timekeeping

AnyTime is a system utility that lets you add multiple clocks to your Mac.

Timer Boom is a free multi-purpose timer application.

TimerTrek is a great Star Trek-inspired timer and countdown clock

Stops apps from quitting unless you hold down ⌘Q for a short delay.

Track elapsed and remaining time between various events.

LunarCal provides the Chinese, Japanese, and Korean calendar on your menu bar.

SleepyTimer - Automate your Mac's status using timers.

Set time limits for specific activities.

Mac app designed to track and reduce your digital distractions.

Automate and schedule computer shutdowns and restarts.

Time Zones allows users to scan preset cities around the world, for their current times.

Candles lets you easily manage birthdays and anniversaries in iCal.

WhiteClock is a nice white clock that will be placed on the black menubar.

TimePlus app has a Digital Clock, 2 Alarm Clocks, 2 Countdown Timers, and more.

Simple app for OS X Mountain Lion that creates Reminders...

Little application that displays calendars on the desktop of your Mac.

Customizes and changes the time and data parameters of files.

Simple todo management software. It is very easy to use. It features cloud syncing.

Monitor the time directly from a Mac desktop.

Pro Timers has 12 simultaneous Countdown Timers and 8 simultaneous Stopwatches