Time Adjusting - NTP, UTC, GMT

Articles about Time Sycronization:

Time adjust in Linux, using ntpdate command; Similar; Using NTPD;  File for using NTPD command ; In this link, details about the NTPD command and the files that  it uses.

Brazilian Time servers:

ntp.usp.br (USP, Stratum 2, São Paulo, SP); ntp.hiway.com.br (Stratum 2, Valinhos, SP); a.ntp.br, b.ntp.br , c.ntp.br (Oficcial Public Brazilian Timeservers, Stratum 1); ntp.puc-rio.br (PUC, Rio de Janeiro, Stratum 2); ntp.cais.rnp.br (RNP, Brasilia.Stratum 1. other servers in: RNP); ntp.on.br, ntp2.on.br ( Observatório Nacional, Precise standard, Stratum 1); br.pool.ntp.org (Pool of  the Official Brazilian Time servers); south-america.pool.ntp.org (South-America Pool of servers). 

STRATUM: Stratum 1 servers are those syncronized directly with the standard clock, for example by GPS. To these, are connected secondary servers (very accurate!). Servers of Stratum 3 and Stratum 4 are in  general internal servers, and are obsolete for regular public acess or use in time syncronization.

You may see all the time servers in the Oficcial Home-Page of the NTP  protocol, and in This page

In windows, is intuitive to Syncronize  time, under Linux, use NtpDate ou Better NTPD.

The adjusting of the Time and Date is enclosed  in my Home-Pages, since is important for Science and for Amateur Radio and Computers.

In a simple manner the Time should be measurated with precision, in scientific and technical equipaments.

Anciently, the Official Time in  World, was based on the hour of the "Big Ben" Clock,London, England and was -so-called:

GMT Time, the time of the Greenwich Meridien.

Now, the reference time is called UTC ("Universal Time, Coordinated"),and based on special "Standard Clocks" that uses the atomic vibration of the metal Cesium, as base time.

In Brasil, the reference Time is UTC-3h, "Hora Oficial do Brasil" ou "Horário de Brasília",  and the time reference is "ON-Observatório Nacional", Rio de Janeiro.

In the 80s and 90s, the use of special software, time clients (more Time Clients anf again more), was necessary (I used so much the Nice Tardis 2000), but now the Operational Systems, Windows, Linux os MacOS, are able to syncronize the time of the comp, using several NTP ("Network Time Protocol") servers .

Another process for "taking" the stardard time, is using GPS (for example in QClock).

Symmetricon, a company of NTP servers, produce Symmtime, a good time client and analog clock for Windows