Time is Ticking Away

....and You Are Even Older Than You Think !

National metrology institutes (the preferred phrase for national standards laboratories these days) around the world collectively contribute to maintenance of time through a "virtual clock" managed by the International Bureau of Weights and Measures (BIPM), near Paris. Agilent 5071A Primary Frequency Standards (and its predecessor, the HP5061A/B) represent the majority of the (about) two hundred clocks that are intercompared and mathematically combined to form a standard timescale known as International Atomic Time (TAI).

However, mankind's traditional timescale has been linked to astronomical observations like the period required for the Earth to rotate on its axis (day) or for one orbit of the sun (year). The problem is that these intervals are actually rather irregular, meaning an inconsistent difference between astronomical time and TAI. Hence, although the relentless TAI is ideal for scientific purposes, its everyday use could eventually result in our having mid-day lunch at night !

Consequently, a modified timescale known as Coordinated Universal Time (UTC) is generated that is based on TAI but which is periodically adjusted so as to maintain it within 0.9 seconds of the observed astronomical time at the zero longitude meridian by adding or subtracting whole seconds. The International Earth Rotation Service ( yes, there really is someone responsible for this momentous task !! ) decides whether these "leap second" adjustments are necessary to our clocks and watches.

Since its introduction in 1972, UTC has been regularly modified through inclusion of positive "leap seconds". The cumulative effect is that UTC is now about 30 seconds "behind" TAI so, assuming you were born before that date, you are actually 30 seconds older than you thought !

Additional Material

Further details of Agilent Technologies' contribution to maintenance of international timekeeping can be found in several Application Notes, particularly AN1289.

• Application Notes
  

• BIPM time section
• International Earth Rotation Service
• US National Earth Orientation Service explain Leap Seconds

Did You Know....?
The British civil time scale known as Greenwich Mean Time is, in the most common usage of the term 'GMT', identical to UTC but it has another definition as explained in an article by Professor R.B.Langley of Canada's University of New Brunswick.

• Greenwich Mean Time & Universal Time