How to track Time spent to close a ticket

[Amanda Williams]

I'm trying to find a way to track time spent to close a ticket, but rather than tracking from the created time I'd like to instead track from the assignee field. Many of the cases in this project are created hours before people come in, so tracking from the created time will throw off metrics. 

[Nic Brough _Adaptavist_]

Start by defining what you want the "start" time to be - how are you recording that?  "Assignee" is not a time field, it holds an account.

[Amanda Williams]

Is it possible to track an updated field that corresponds to the assignee change? My entire problem is figuring out a time field to track.