How is disk activity time calculated ?

Dear community,

When I run HP SMART Insights utility and diagnose my disks, it says that such disk has X months of activity.

Is activity = age ?

Suppose I bought a disk 5 years ago but only used it for 1 week, 2 years after it came out of the factory.

What would the activity time be : 1 week, 3 years or 5 years ?

Sorry if stupid question but we have some disks with 40+ months of activity we would like to know if the counting is simply current date - date of first usage or is the activity time calculated on actual I/O traffic..

Thanks for any answer.

ascii sutpid question, get a stupid ansi.