Open the 
Item Tracking
Codes window.
Create a new item tracking code or select an existing.
Click Item Tracking Code, Card.
On the Misc. tab, fill in the Warranty Date Formula field and check mark the desired fields.
For some items, you might want to set up specific warranties in the item tracking code. This functionality allows you to keep track of when the warranties on specific serial/lot numbers in your inventory will run out.
Open the Item Tracking
Codes window.
Create a new item tracking code or select an existing.
Click Item Tracking Code, Card.
On the Misc. tab, fill in the Warranty Date Formula field and check mark the desired fields.
Press F1 to see online help for the individual fields
Setting Up Expiration Rules for Serial/Lot Numbers
Setting Up Item Tracking Codes