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Wireshark-bugs: [Wireshark-bugs] [Bug 3695] Wrong decoding of timestamp in DNP3.0

Date: Sun, 30 Aug 2009 06:34:09 -0700 (PDT)
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=3695


Rob Casey <robc@xxxxxxxxxxxxxxxxx> changed:

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--- Comment #4 from Rob Casey <robc@xxxxxxxxxxxxxxxxx>  2009-08-30 06:34:05 PDT ---
>From DNP3Spec-V5-LayerIndependent-20071215:


3.2 Time Base

DNP3 time corresponds to Universal Coordinated Time, UTC1.

UTC does not shift with daylight saving (summer) time and does not change
depending upon the local time zone. Thus, events that occur at separate
geographical locations, but at the same instant are reported with identical
DNP3 time values.

UTC, and therefore DNP3 time values, are adjusted appropriately when leap
seconds are added or subtracted by IERS, International Earth Rotation Service -
http://www.iers.org/ so that UTC agrees with astronomical time based on the
rotation of the earth.

Values within DNP3 time objects contain the number of milliseconds from the DNP
time epoch, which is defined as 1970-01-01T00:00:00.0002 UTC. The DNP time
epoch assumes there were exactly 86,400,000 milliseconds in every day during
the intervening years; i.e., it does not include leap-seconds.


In short, it can be expected that DNP3 time stamps will be "incorrect" where
times there is a difference in system time zone configuration and times are
referenced to the local time zone.  Accordingly, care should be taken to either
match local system time zone with that of the source DNP3 host(s) or to
undertake interpretation relative to UTC. 


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