Time since creation
Return the days that have passed since the creation of the current work item.
Configuration
Create a Custom smart number field and use the General parsing mode.
Expression
%{floor(({system.currentDateTime} - {issue.created})/DAY)}
The duration can be retuned in years, weeks, days, hours or minutes if the DAY keyword is replaced in the above expression with the corresponding time constant.
Format
Default
Used parser functions
The links lead to the JWTC documentation because the parser functions are shared functionalities.