Standard Time of Sri Lanka

Set your Computer time Synchronized with NTP Server at  Measurement Units, Standards and Services Department(

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Standard Time Regulation 2011




Here you find answers to questions about time which are frequently asked. Please click on a question from the list below to call the answer:

 What is time?

What is a second?

What is NTP: Time via the Internet ?

What is an Atomic clock?

 What is time?

about space into questions about time, questions that have their roots in the works of early students of natural philosophy.

Among prominent philosophers, there are two distinct viewpoints on time. One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence. Sir Isaac Newton subscribed to this realist view, and hence it is sometimes referred to as Newtonian time. Time travel, in this view, becomes a possibility as other "times" persist like frames of a film strip, spread out across the time line. The opposing view is that time does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instead part of a fundamental intellectual structure (together with space and number) within which humans sequence and compare events. This second view, in the tradition of Gottfried Leibniz and Immanuel Kant, holds that time is neither an event nor a thing, and thus is not itself measurable nor can it be travelled.

Temporal measurement has occupied scientists and technologists, and was a prime motivation in navigation and astronomy. Periodic events and periodic motion have long served as standards for units of time. Examples include the apparent motion of the sun across the sky, the phases of the moon, the swing of a pendulum, and the beat of a heart. Currently, the international unit of time, the second, is defined in terms of radiation emitted by caesium atoms . Time is also of significant social importance, having economic value ("time is money") as well as personal value, due to an awareness of the limited time in each day and in human life spans.

Ray Cummings, an early writer of science fiction, wrote in 1922, "Time is what keeps everything from happening at once", a sentence repeated by scientists such as C. J. Overbeck,and John Archibald Wheeler.

 What is a second?

To most of us it is absolutely clear that one second is the 60th part of a minute, one minute the 60th part of an hour, and one hour the 24th part of a day.

Physicists, however, don't find this good enough. In their opinion, the day (to be more precise: the duration of one complete rotation of the earth) is not a good measure of the unit of time because the earth does not really turn as uniformly as one might think. Not only has the "mean solar day" lengthened over the centuries; but there also occur periodical (seasonal) and non-periodical variations. Therefore, in 1967, the second - as one of the base units in the International System of Units SI - was defined in terms of atomic physics:

The second is 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 caesium-133 atom.

What is NTP: Time via the Internet ?

The MUSSD operates two time servers for the time synchronization of computers via the Internet. For disseminating time information, these servers use the "Network Time Protocol" (NTP). The design of this protocol aims at synchronizing computer clocks within LANs and throughout the Internet. It is based on the Internet IP protocol and is available for all relevant operating systems.

Synchronizing a computer by means of the MUSSD time servers requires adequate software supporting this protocol. Such programs are available for the Windows, UNIX, Macintosh and other operating systems. A list of suitable programs can be found at "Time Synchronization Software" . After installing any such program it must be given the addresses of servers to be used for time synchronization.

What is an Atomic clock?

Very accurate clocks can be constructed by locking an electronic oscillator to the frequency of an atomic transition. The frequencies associated with such transitions are so reproducible that the definition of the second is now tied to the frequency associated with a transition in cesium-133:

1 second = 9,192, 631,770 cycles of the standard Cs-133 transition

The two most widely used atomic clocks in recent years have been the cesium beam atomic clock and the rubidium clock. Such clocks have provided the accuracy necessary to test general relativity and to track variations in the frequencies of pulsars. Atomic clocks are integral parts of the Global Positioning System since extreme accuracy in timing is necessary for the triangulation involved.

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