About having a precise clock

Throughout history time on earth has been measured by studying the movements of the sun in the sky.
The time it takes the earth to travel around the sun is called a year.
Seen from the earth a measure point can be established, for instance summer solstice where the sun reaches its highest point
during the year at noon. The time it takes before the sun is back to the same position can be defined as one year.
The year can be split into days (about 365.25 each year, the quarters making a leap day every four years).
Day-and-nights are split into 24 hours, each with 60 minutes of 60 seconds.
In other words, 31,557,600 seconds is the time it takes for the earth to orbit the sun.

But nowadays seconds are not measured this way.
Instead, 1 second is defined as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition
between the two hyperfine levels of the ground state of the cesium 133 atom".
By using atomic clocks time indication has become extremely precise.

Copenhagen

Point zero of the modern scale (UTC, Universal Time, Coordinated) is identical to Greenwich at midnight.
The clock to the left is (via the internet) directly connected to World Time Server,
constantly feeding the pointers with the exact hour of the actual time-zone, in this case: Copenhagen
(CET, Central Europe Time). CET is 1 hour ahead of UTC (UTC+1), 2 hours ahead (UTC+2) in case of daylight saving.

A digital version of the Copenhagen-time can be seen at http://time.is/Copenhagen.

Below the clock you see a green digital time, probably not identical to the indication of the round clock.
This is the local time of your computer, generated from a chip on your motherboard.
If the difference is too significant, you may consider adjusting the local time.

Steen Juhler  < This red dot is turned on and off every second in accordance with your computer clock