I have a handful of tickets which have start and end dates, and estimated hours.
The chart is ignoring/over-riding the start date to calculate its own.
But in doing so, it ignores weekends.
So I have a ticket with start date 2012-01-09 and finish date 2012-02-17
and 150 hours estimated. But when I draw a chard with hoursPerDay=7,
it shows up on the chart as end date 2012-02-17, start date 2010-01-27.
So the duration has been reduced to 22 days elapsed, which is 149 hours if you work seven days a week.
If I reduce "hoursPerDay" to 5, the start day is pushed to the 19th of January. 30 days at 5 hours per day, 7 days per week.
So contrary to what it says at http://trac-hacks.org/wiki/TracJsGanttPlugin
this is taking no account weekends.