Steps to reproduce:

1. For example, set the time on the host (we had a problem on Windows Server 2016 x64) to 09/08/1868
2. Create an item for this host with the key system.localtime and the unit unixtime
3. Create some trigger that will work on the data of this item
4. Open the dashboard, where the event will have the value of this item in the operational data. You can also try to open the latest data on this item.

Result:
Screenshot of what it looks like in UI:

How it looks in the application log (example from the log from a full bootloop cycle  ):
zabbix_server.log-20250731