A $300,000 watch? Luxury. A $300,000 watch that doesn't tell time -- and that sells out? Pure genius.

According to several news reports flagged by my friends at Luxist, Swiss watchmaker Romain Jerome just launched the "Day&Night" watch. The watch won't tell you what time it is. That's so yesterday. But it does tell you whether it's day or night -- helpful, I guess, for billionaire types who can't afford windows.

The Day&Night watch (Romain Jerome)

As the company's Web site boasts: "With no display for the hours, minutes or seconds, the Day&Night offers a new way of measuring time, splitting the universe of time into two fundamentally opposing sections: day versus night."

What's most impressive about the Day&Night is its complexity, given its absolute uselessness. The watch features two tourbillons -- devices that overcome the ill effects of earth's gravity on a watch's accuracy -- connected by a differential mechanism. Instead of hands, the watch has a "contemplative tourbillon operation whereby the 'Day' tourbillon operates for 12 hours to symbolize working life, while the 'Night' tourbillon takes over afterward to represent an individual's private time."