Diferent Timestamp Webpage and server

Graylog saves all dates in UTC format, and shows it in GUI in timezone configured for particular user.

  1. For user admin, it uses timezone defined in /etc/graylog/server/server.conf file, parameter root_timezone.
    root_timezone = Europe/Bratislava

Change Europe/Bratislava to your real timezone, and restart graylog server.
https://docs.graylog.org/en/3.1/pages/configuration/server.conf.html#general

  1. For other user accounts other than admin, configuration is done in GUI. Every user can change their Time zone in their User Profile, or admin can change it also in System - Authentication - Users - Edit, field Time Zone.
    https://docs.graylog.org/en/3.1/pages/users_and_roles/users.html#timezone