[ntp:questions] Re: ntp packets

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Thu Oct 30 10:18:25 UTC 2003

On 27 Oct 2003 03:26:46 -0800 in comp.protocols.time.ntp,
karlobrien2 at yahoo.com (moorefieldman) wrote:

>I have written a java program to request the time off an NTP server.
>What I get back from the ntp server is the following:

>52939 03-10-27 11:17:23 00 0 0 387.7 UTC(NIST) *

>I was wondering if anybody could tell me what each field stands for, I
>know the time and date are there but what do the others mean?

It's the NIST dialup ACTS time format:


probably provided from NIST via the Daytime protocol:


AFAIK nobody else uses this format:


	JJJJJ is the Modified Julian Date (MJD). 

	TT is 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 will decrement every day until the change

	L is a one-digit code that indicates whether a leap
second will be added or subtracted at midnight on the last day of
the current month. If the code is 0, no leap second will occur
this month. If the code is 1, a positive leap second will be
added at the end of the month. If the code is 2, a second will be
deleted on the last day of the month. The correction is made just
before midnight UTC (not local time).

	H is a health digit that indicates the health of the
server. If H=0, the server is healthly. If H=1, then the server
is operating properly but its time may be in error by up to 5
seconds. If H=2, then the server is operating properly but its
time is known to be wrong by more than 5 seconds. If H=4, then a
hardware or software failure has occurred and the amount of the
time error is unknown.

	msADV displays the number of milliseconds that NIST
advances the time code to partially compensate for network
delays. The advance is currently set to 50.0 milliseconds.

	UTC(NIST) is contained in every time code. It indicates
that you are receiving Coordinated Universal Time (UTC) from the
National Institute of Standards and Technology (NIST).

	OTM (on-time marker) is an asterisk (*). The time values
sent by the time code refer to the arrival time of the OTM. In
other words, if the time code says it is 12:45:45, this means it
is 12:45:45 when the OTM arrives. 

Thanks. Take care, Brian Inglis 	Calgary, Alberta, Canada
Brian.Inglis at CSi.com 	(Brian dot Inglis at SystematicSw dot ab dot ca)
    fake address		use address above to reply

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