Symmetricom Time Server Manual Do Utilizador

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The Automated Computer Time Service (ACTS) is run by the National Institute of 
Standards and Technology (NIST) in Boulder, Colorado.

ACTS allows computer users with modems to synchronize their clocks by telephone. The 
phone number for ACTS is (303) 494-4774 (not toll free).  Users can connect at speeds of 
up to 9600 baud with 8 data bits, 1 stop bit, and no parity and obtain time signals with 
standard uncertainty of 5 ms.  To receive the full time code, you must connect at a speed 
of at least 1200 baud.  

The full time code is transmitted every second and contains more information than the 
300 baud time code, which is transmitted every 2 seconds. The full time code looks like 
this:

JJJJJ YRMODA HH:MM:SS TT L DUT1 msADV UTC(NIST) OTM 

where

JJJJJ

=

the Modified Julian Date (MJD).  The MJD is the 
last five digits of the Julian Date, which is the 
number of days since January 1, 4713 B.C.  To get 
the Julian Date, add 2.4 million to the MJD.

YRMODA

=

the date, showing the last two digits of the year, the 
month, and the current day of month.

HH:MM:SS

=

the time in hours, minutes, and seconds.  The time is 
always sent as Coordinated Universal Time (UTC). 
An offset needs to be applied to UTC to obtain local 
time.  For example, Mountain Time in the U. S. is 
7 hours behind UTC during Standard Time, and 
6 hours behind UTC during Daylight Saving Time.

TT

=

a two digit code (00 to 99) that indicates whether the 
United States is on Standard Time (ST) or Daylight 
Saving Time (DST).  It also indicates when ST or 
DST is approaching.  This code is set to 00 when ST 
is in effect, or to 50 when DST is in effect.  During 
the month in which the time change actually occurs, 
this number decrements every day until the change 
occurs.  For example, during the month of October, 
the U.S. changes from DST to ST.  On October 1,