Widgets have last 7 days selected as the timeframe.
The Average time to closure widget is added to the dashboard and the timeframe set for it is last 7 days, then it is calculating the average from looking at the time to closure (realtime) metric for incidents closed within the last 7 days (24 *7 = 168 hours).
This does not work for service desk that work standard 40 hour weeks (no weekend cases). I assumed the point of having working hours set in profile would account for this however, this is for SLA.