Just for a Update I made a test with the graylog server changing the timezone from Linux (graylog was always restarted when I changed linux timezone)
2017-01-04 17:41:56.000 - The graylogserver was in BRT Timezone After that time 2017-01-04 17:41:56.000 I stoped graylog server changed the timezone to UTC and the graylog stoped to recivied the messages from this timezone BRT client ( I made tests with logger too), but start to recivied messages from the others clients with UTC timezone. I waited to change again because I hoped the messages will take at least 03:00 hours to "show" on graylog console, but nothing happaned. So today I changed again to BRT and after that I started to recive messages as you see on 2017-01-05 08:17:58.000 -- You received this message because you are subscribed to the Google Groups "Graylog Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to graylog2+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/graylog2/77cd2b81-41b2-4467-bfd0-d61131d93919%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.