Approach for Defining Time Durations in Business Days

I’d like to put a suspense on a user activity that’s expressed in days, for example:

    <boundaryEvent id="userTaskDeadline" attachedToRef="myUserTask">

This works great, but it doesn’t take into account business days. So if the task is assigned on Friday, the deadline will expire before the user has a chance to address it on Monday. Is there a way to express a day-based duration (ISO-8601 or otherwise) that excludes weekends?

Business calendar is not an easy topic. Weekend in Israel differs from the weekend in US…
You can implement your own business business calendar to handle your requirements.