You can create dynamic Gantt Charts or Timelines using pure PowerBuilder logic with text controls inside a tabular DataWindow, drawing grid lines for time periods with major lines and minor lines (sub-divisions) and setting X, Width, Color (text color, bar color), scaling factor, etc. for text bar controls as dynamic expressions using dynamic data. I did it once and also added a Today date-line and made it reusable. If you wanna make your DW-based timeline chart reusable, you prolly want it to be an External DW and insert dynamic data into it manually at runtime using a datastore, etc.
However, there is now an easier and a more elegant way to implement Timeline charts using the integrated Google Charts in PB (without using DW). Check out the w_Timelines window in GoogleCharts target inside Example Graph App workspace from Appeon along with all the PowerScript code. Run the target to view the chart.
You can also install and run the compiled PowerBuilder/PowerServer demo versions from here -
https://demo.appeon.com/?powerbuilder
Run the GoogleCharts target -
HTH