Here's how you may add a column in structure to report issue age / resolution time for each issue row using formula. Please note that the age is in days in below formula. I hope that helps:
if resolution=undefined:
concat(days_between(created,today())," d")
else:
concat(days_between(created,resolved)," d")
Here’s how the the calculation works for the Issue aging as per JIRA Community of Practice:
Meaning, Issue Aging will be stopped as soon as it is resolved.