Good afternoon.
My graylog on the web has the wrong time for where I get it.
If you login as admin to graylog GUI, check parameter root_timezone in /etc/graylog/server/server.conf and setup correct timezone:
sudo vim /etc/graylog/server/graylog.conf
root_timezone = Europe/Bratislava
After that restart graylog:
sudo systemctl restart graylog.service
If you use another user, check your User Profile (top right corner icon) and choose appropriate Time Zone. As a admin user you can also change Time Zone parameter for another user in System - Authentication - Users - Edit - field Time Zone.
If none helps, you have probably problem with timestamps from devices.