Uplink time is in UTC format

ChirpStack Network Server
1

Hello,

I noticed a strange behavior on the uplink timestamps.
I am using Chirpstack Version: v4.9.0
For Gateway I am using:

  1. RPI CM4 + RAK2287
  2. RAK7289CV2

I tested with several different end nodes.
I also tried using UDP and MQTT forwarder.

So here is the issue:
For uplink messages I see UTC time and for downlink it is GMT+4 (my region).
Server is a VM and in chirpstack logs timestamp is ok.

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System time is set correctly:

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Here is one frame which shows correct time in the list (21:49), however inside the decoded data it says gwtime 17:49 (not correct)

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Here is another example, where even the time in the packet list is incorrect > it says 17:49, while it should be +4h

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I checked time on both GWs and it is correct, f.eg:

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Is there explanation for this behavior?

2

Please note that the JSON view of the packet is rendered server-side (and explicitly says +00:00 indicating it is UTC / no offset).The timestamp in the table view is rendered by the browser and follows the timezone of your computer.

3

Hello Brocaar. regarding table view, since it is rendered by my PC/Browser, then it should be incremental, following the time of my PC. But here f.eg sometimes it shows 21:47 and then immediately after next packet it shows 17:47 (4 hours back), then after some packets it again shows 21:49. How this can be explained?

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4

Hello, I don’t know what happening, but in the image the difference appears when the DevAddr is different, it’s can be related.

5

@andrelquiosi yes correct, but if this time is generated by browser then it is strange why some device uplink is in UTC and some is in UTC+4. Btw both devices were sending uplink to the same gateway

6

What I recall is that this list uses the time from your gateway. There are multiple methods for a gateway to get the time, which could be the use of GPS or its RTC. The exact timezone used by the gateway isn’t important, as all time on this planet is consistent. It’s internal to the data flows linked to the gateway.

So are you saying that the time is wrong, and it’s not actually a timezone problem?
If so, then does your gateway have Line of Sight with the sky, since it has a GPS?

If you cannot guarantee that its GPS function can work, do you have this setting enabled?

  # Time fallback.
  #
  # In case the gateway does not have a GNSS module or is unable to aquire a
  # GNSS fix, use the system-time for setting the 'time' field on RX.
  time_fallback_enabled=true
7

Hi @sp193 , I am not using GPS, but since GW has internet it is relying on NTP server. Strangely this problem disappeared now. Perhaps this topic can be closed and I will reopen if I see the problem again

8

I still think you should have this setting enabled, if you do not already have it enabled.

The normal workflow is to use the GPS, even if there is a NTP server for maintaining the RTC’s correctness.