Basically, this thing shows only times that are prime numbers and blinks red when it finds a “special” prime like a Sophie Germain Prime. Sophie Germain, I believe, starred in Get Smart. Great photo.

While not as precise as a radioactive-cesium timepieces, The Time Prime Clock expands substantially on the accuracy of a broken clock. As Lewis Carroll pointed out, stopped clocks are accurate twice a day – but the time prime clock can boast 7661 moments of reasonable accuracy every 24 hours — starting with 00:00:02 and ending with 23:59:51.

Since there are an average of about three primes per minute — you shouldn’t blame the clock for being late.

Primes are the numbers that are evenly divisible by themselves and one; 2 and 3 are prime. 4, because it’s evenly divisible by 2, is not.

There are 20903 primes between 0 and 240000. But remember, most of those numbers are not TIME primes. 22:89:01 is a time only in Wonderland.

More here.