Archive for February, 2009

UTC Time Zones Explained

Coordinated Universal Time or UTC is now the world’s time standard it took over from the old Greenwich Meantime (GMT) after the development of atomic clocks. UTC is based on GMT but accounts for the random variations of the Earth’s rotation by having leap seconds added once or twice a year.

By accounting for the Earth’s rotation, UTC can keep noon above the meridian line (as GMT) but can also be recorded by the highly accurate atomic clocks.

UTC is ‘Universal’ in that it allows the entire world to communicate with the same timescale. For us humans UTC accounts for the time-zones by having a positive or negative integer after the time. Here is the UTC time zones:

world_time2

Fortunately computers aren’t bothered about timezones and when communicating together across global networks via a time server UTC is the same no matter where they are on in the world.

Computer time servers usually receive their UTC time from a source external to the internet such as the GPS signal which are directly broadcast via atomic clocks in doing so a time server can keep a computer network to within a few milliseconds of UTC.

Time server – Using NTP for Synchronisation

A time server is a generic term for a device that receives and distributes time.  Time servers are available across the Internet or dedicated devices can be bought that offer higher accuracy and more security.

Whilst many manufacturers produce time server devices and other synchronisation tools they all have one thing in common in that they all utilise Network Time Protocol (NTP).

Whilst NTP is not the only time synchronisation software available it is used in the vast majority of synchronisation tools with some 99% of time synchronisation being conducted using NTP. NTP is a protocol used by everyone from NASA to NASDAQ and owes much of its dominance or the time synchronisation market to the dedicated team that continue to update, upgrade and develop NTP (many of whom do not get paid).

NTP is in fact almost as old as the Internet itself having been unveiled as early as 1979. It was developed by Professor David Mills and his team from Delaware University who continue to update and develop it alongside hundreds of dedicated hobbyists referred to as the Internet timekeepers.

NTP is now on version 4 and versions of NTP are included as standard with most operating systems allowing any Windows or Linux computer to run as a time server. However, for those serious about time synchronisation or wanting to keep a network secure there is no real substitute than a dedicated time server that can distribute time sent directly from an atomic clock using NTP.