if the devices do not send a timestamp with timezone information included it is always a mess…
But what kind of normalization, pipelines or extractors did you use with that messages? Because timestamps without any timezone information are UTC for Graylog.
There are currently no extractors on the input or any associated pipelines.
This is a new input.
Like I mentioned before another Cisco device is processing properly where Graylog is assuming the time it extracts as UTC. Funny thing is the FirePower module message format is nearly identical to the ASA with the exception of the year is missing in the timestamp.
ASA message: <157>Mar 28 2019 11:19:38 ASA : %ASA-5-611103: User logged out: Uname: user
Has Graylog timestamp of: 2019-03-28T11:19:38.175Z