LLH output time

Reach RS2 running ReachView v2.20.8

I am reading position output from TCP with LLH format and I’m puzzled by the timestamp there. An LLH line entry looks something like

2019/12/11 09:41:44.400 50.123456 1.2345678 51.7700 0 0 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.40 0.0

I see that the timestamp is about 17-18 seconds ahead of the system clock on the device itself (as seen by ‘date’ util over ssh). I found the same timedelta on an Android tablet reading LLH entries over TCP (comparing latest LLH entry with tablet internal clock). Is this expected? Why is it so? I see a consistent time shift here both with and without GNSS satelite coverage.

The LLH documentation from RTKLIB manual v 2.4.2 says:

The epoch time of the solution indicating the true receiver signal
reception time (not indicates the time by receiver clock)

Does that in any way explain why I’m seeing a 17-18 second forward shift here?

You could be seeing the difference between UTC and GPS time

The GPS navigation message includes the difference between GPS time and UTC. As of January 2017, GPS time is 18 seconds ahead of UTC because of the leap second added to UTC December 31, 2016. Receivers subtract this offset from GPS time to calculate UTC and specific timezone values. New GPS units may not show the correct UTC time until after receiving the UTC offset message. The GPS-UTC offset field can accommodate 255 leap seconds (eight bits).

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Ah, that must be it. Thanks

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