Set theory clock in Berlin - how to read the clock?

One of the most interesting clocks in Berlin is the “Mengenlehreuhr”(set theory clock) or “Berlin Clock”, which has certainly driven numerous viewers to despair.

I can still remember how this clock stood at the intersection of Kurfürstendamm and Uhlandstraße and drove me almost to despair as a child. It was supposed to be so easy to tell the time.

The Berlin Clock was developed in 1975 by the inventor Binninger on behalf of the Berlin Senate. It is the first clock in the world to show the time with luminous coloured fields and is thus also in the Guinness Book of Records. At that time, digital clocks were hardly widespread and small replicas quickly found their way into households.

The colourful fields of the clock were illuminated with incandescent lamps and was quite high-maintenance. In 1991, Binninger died and the maintenance costs now had to be borne by the city. However, the city did not want to bear the costs and so the clock was retired in 1995. Business people decided to take over the costs and put up the clock at the Europa Center.

The set theory clock is quite hidden there and has almost been forgotten by the Berliners.

What time is it now?

The time display actually has nothing to do with set theory. It takes place in a place value system on base 5.

There are four lights in the first, second and fourth rows and eleven lights in the third row. Above the rows is a round flashing light that lights up every 2 seconds.

The hours can be read from the first two rows that are lit up in red. The upper row shows 5 hours per lit field. In the bottom row, one field lights up per hour. If you look at our photo, you see 3 illuminated fields at the top and 2 illuminated fields below. Now you just have to calculate: 5+5+5+1+1=17
So it is 17 o’clock!

Next, determine the minutes. To do this, read off the two bottom lines that are lit in yellow. The four large fields correspond to one minute each. The small, narrow fields (there are 11 of them) each correspond to 5 minutes. To make it easier to read off, the lights for 15, 30 and 45 minutes are red. If you now look at our photo, you can see (apart from a broken red lamp) that 6 narrow fields and no large field are illuminated. Now you can calculate again: 5+5+5+5+5= 30
So there are 30 minutes!

Now combine the results from both calculations and get the time: 17:30!

Have fun calculating and reading off the time!