TimerTrek is a great Star Trek-inspired timer and countdown clock. If you have ever watched a Star Trek movie, you probably have noticed the graphical interfaces of the computer terminals on the starships. They have looked pretty much the same since Star Trek: The Next Generation. TimerTrek puts that interface on your Mac so that you can use a timer or countdown clock.
By default, the application is opened in full-screen mode, but you can switch to windowed mode by clicking on the screen. The timer starts at 0 and if you click on start, you will activate the timer function. If you want to use a countdown clock, you have to set the starting time by clicking on the hours, minutes and seconds buttons. The countdown is started the same way as the timer. There are other buttons on the screen that do different things. For example, the "nano" button will activate a nano timer, which is basically a small window with your timer in it. You can mute the app and change the interface sounds with other buttons.
At the top of the screen, there is the current time and stardate, which you can change to the current date by clicking on it.
In short, if you are a trekkie and in need of a timer, I don't think there is a better choice than TimerTrek.