This can be done already with the existing functionality.
You need a trapper item and a trigger. No manual entries in the HW inventory field though.

1. Create a trapper item.
2. Make sure you send the item value as UNIX timestamp and display the unit as unixtime
   
3. Create a trigger for this item which takes the unixtime value of the trapper item and compare it to the current time. Then alert if the change is less than your desired time period in seconds. As example 14 days.

   {Template ZBX Test:hw.warranty.last()} - {Template ZBX Test:hw.warranty.now()} < 1209600
   

   

Closing, as solution to the problem is proposed.

If the problem is still present, please, reopen the issue.

Ok, porém de onde você está coletando o vencimento da garantia do Hardware?

Não seria mais fácil, coletar esta informação do inventário?

Em vez de popular o inventário automáticamente, esta informação é populada manualmente, e usa esta informação para gerar alertas no próprio zabbix.

 
Okay, but where are you collecting the warranty expiration from Hardware?

Is not it easier to collect this inventory information?

Instead of populating the inventory automatically, this information is populated manually, and uses this information to generate alerts in zabbix itself.