"Prague time" abolished 95 years ago


The Czech Republic, like most EU countries, uses Central European Time. But few people know that until 1912, the Czech capital Prague had its own time zone. The so-called "Prague time" was 2 minutes and 18 seconds behind the rest of Central Europe. The clocks were finally synchronised 95 years ago this week.

Prague's historic Klementinum library is where Prague time used to be measured, just a few hundred metres away from the Prague meridian - which you can see to this day marked in the paving on the Old Town Square. Once the shadow of the column dedicated to Virgin Mary fell on the meridian at noon, the senior timekeeper here in the observation tower of Klementinum waved a flag. At that instance, all the clock keepers on Prague's towers synchronised their clocks.

Libuse Piherova of the Klementinum library told me about the history of timekeeping at the institution.

"Klementinum is a former Jesuit college where many learned men used to live and work. Local astronomers used to measure time here, specifically the 'Prague noon'. In the so-called 'Meridian Hall' on the astronomical tower, there is a chord which physically represents the Prague meridian. When a sun beam entering the hall hit the chord, the monk on duty in the room sent a signal upstairs and another one on the top floor waved a flag."

Besides the waving which started in 1842, another time signal was added in 1891 - a gun shot at midday from the ramparts on Letna and later near Prague Castle. After the so-called "Prague time" was finally abolished on January 1st 1912, the waving continued although the 'Prague noon' was adjusted to Central European Time.

"The flag waving was finally abandoned in about 1926. But even in modern days, Klementinum was an important timekeeping institution. There was a very accurate clock here whose signal was transmitted on the waves of the Radiojournal station which started broadcasting in the 1920s."

Today, time measurement is a task for physicists rather than astronomers. At present, precise time in Prague is measured by an atomic clock located at the Institute of Radio Engineering and Electronics in the north of the city. Since 1969, the country's central clock has been coordinated with universal time. The official title of the time is UTCTP, or Universal Time Coordinated Tempus Praguensae and this is identical to Central European Time.