RE: change bar width according to timestamp in reporting module

That's not how column bar charts work. Each column represents one X-axis time period or category.

  1. How will you display if the machine runs for 30 minutes?
  2. What does the height of a bar mean?

Normally you would use a horizontal bar chart for this and "stack" the time periods left to right. There's an example in Ribbon chart in Ignition Reporting module.