Time with agent

Summary: What is the best way to calculate the time the case has been with an agent?

Content (required): For example, when a client raises a case it gets assigned to an agent. The agent then works on it for 2 weeks but then has to transfer it to another agent for 4 weeks, eventually, the case gets passed to a senior and they have it for 1 week. I need a way to show how often the case has been with an agent with a column to show day, hours, and min.

Version (include the version you are using, if applicable):

21D SP5