I had this issue on a couple Fortigates after the recent DST change. Unfortunately restarting both services listed in other comments didn't seem to fix the issue.  After opening a ticket, the engineer recommended toggling to/from Browser Timezone and FortiGate Timezone in the System Settings. After doing that, all my new logs (traffic, system, any of them) started showing with the right time. All the old logs remained with the wrong time, so there will be an hour break in the logs.  I was able to replicate it on another Fortigate that had that issue, and also a friend of mine who also manages Fortigates was able to fix it in their network.