Hi,
...me again....
Now, I did some further testing. I created a fieldnotes.txt file as an export from Locus Fieldnotes plugin.
This is the contents:
GC6G8M2,2016-11-24T08:10Z,Found it,"# 7879, 24.11.2016, 09:10 Online Log. Später mehr... Danke für den Cache! Gruß, bigchen."
As you can see, I found it 08:10 UTC, 9:10 MEZ.
Now I uploaded the log using the Fieldnotes Plugin via Locus as fieldnotes and I imported it using the upload function from geocaching.com.
This is the result (first entry from the web site upload, second one from Locus upload):

So, I got a time diff from about 8 hours when sending logs with Locus.
Anyone any idea? If I can do some more testing, just tell me.... ;-)
I also tired to change my time zone in my geocaching.com profile, but this only adjusted the times shown in the field notes list.
Thanks for taking care!
Cheers, big.