Time and frequency

The Norwegian Metrology Service’s National Laboratory for Time and Frequency

The Norwegian Metrology Service’s National Laboratory operates several atomic clocks and participates in the international system for determining global time. We also provide NTP services and calibration assignments. Our laboratory houses five atomic clocks, two hydrogen masers and three caesium clocks, delivering extremely stable and precise time signals.

Coordinated Universal Time (UTC)

Every five days, we send time signals from our clocks to the International Bureau of Weights and Measures (BIPM) in Paris, which calculates the global time scale UTC (Coordinated Universal Time). We regularly receive reports showing tiny deviations between our clocks and UTC, often only a few nanoseconds. This enables us to compute a national time scale that is both more accurate and more stable.
By participating in this global collaboration, we contribute to defining the world’s time – ensuring that Norway has access to reliable and traceable time.

How world time is calculated

BIPM performs the calculation in three stages (from the outside in):

1. Stability
   The large number of clocks worldwide are used to calculate an average that remains stable even if individual clocks drop out or new ones are added.
2. Accuracy
   A handful of “super clocks” in selected countries are used to adjust this average so that one second in UTC corresponds as closely as possible to the SI-defined second. 
3. Leap second
   Approximately every three years, a leap second is introduced to correct for the difference between time based on the Earth’s rotation (UT) and the much more stable atomic time in UTC. The International Earth Rotation and Reference Systems Service (IERS) monitors the Earth’s rotation and announces a leap second when the deviation from UTC approaches one second.

In recent years, an average day has been about one-thousandth of a second longer than exactly 24 hours. The leap second system was introduced in 1972, and the last leap second was added between 2016 and 2017.

In practice, leap seconds ensure that UTC remains synchronised with the Earth’s rotation so that the Sun is at its highest point at the Greenwich meridian within one second of 12:00:00 UTC. Here you can watch NRK Supernytt explain how the day gained an extra second in 2015.

Norwegian time

By law, the standard time in Norway is one hour ahead of Coordinated Universal Time (UTC). This is denoted as UTC+1 or CET (Central European Time). During daylight saving time, Norwegian time is two hours ahead of UTC, expressed as UTC+2 or CEST (Central European Summer Time).
Daylight saving time normally applies from 02:00:00 AM on the last Sunday in March to 03:00:00 AM on the last Sunday in October. The dates for switching between standard and summer time are harmonised across the EEA and decided by the European Commission in accordance with the EU Summer Time Directive.

Daylight saving time and standard time

Daylight saving time is the period of the year when clocks are set one hour forward compared to the rest of the year. It was first introduced in several European countries during the First World War to make better use of daylight during waking hours, saving energy on heating and lighting. Norway has daylight saving time every year since 1980.
Tip for remembering:
In spring, look forward to summer and set the clock one hour forward. In autumn, think back to summer and set the clock one hour back.

Time and satellite navigation

The staff of the Norwegian Metrology Service have high competence in clocks, synchronisation and GNSS (Global Navigation Satellite Systems). This expertise has been used, among other things, in the Jammertest project – the world’s largest open arena for ethical hacking – in collaboration with the Norwegian Public Roads Administration, Norwegian Communications Authority, Norwegian Defence Research Establishment, Norwegian Space Agency, and Testnor.

Atomic clocks in satellites

Atomic clocks are vital components in satellite navigation systems, providing extremely accurate time synchronisation essential for precise positioning. Each satellite in GNSS systems contains atomic clocks that transmit accurate time signals together with position data. These systems, however, are vulnerable to interference.

Jamming and spoofing

Jamming refers to the deliberate interference or blocking of GNSS signals (positioning signals). Spoofing means transmitting falsified or manipulated GNSS signals to deceive the receiver.

The Norwegian Metrology Service’s time laboratory has developed an advanced GNSS simulator capable of transmitting false GNSS signals for controlled test purposes. It is used in the Jammertest project and other research activities.

This work began in collaboration with Statnett and continues today with support from the Norwegian Space Agency. It involves generating and transmitting false GNSS signals that may cause receivers to report incorrect time, position or speed. By testing with both basic and advanced interference, we gain insight into vulnerabilities and help improve the security of satellite-based clocks. This is crucial for critical infrastructure such as power grids and telecommunications.