Well, first you can ignore the nodes and links from that sample.
But notice that there is a “Line” category node template. This contains a Grid Panel (named “BAR”) consisting of only white vertical lines on a lightgray background.
Furthermore there is a Table Panel (named “TABLE”) whose Panel.itemArray is set to an Array of Date objects. The itemTemplate is a TableColumn Panel containing only a TextBlock whose TextBlock.text property is data bound to the Date object.
The TimelineLayout’s execution is what creates the Array of Dates and sets the “BAR”-named Panel.gridCellSize and Panel.gridOrigin and sets the “TABLE”-named Panel.itemArray and RowColumnDefinition.widths.
If you are just getting started with GoJS, this may be a bit overwhelming. I highly recommend that you first read http://gojs.net/learn and then http://gojs.net/intro and all of the Introduction pages that seem relevant to your app.
We have considered creating a timeline component in GoJS, which might make it easier to understand what you can fiddle with and what is an internal implementation detail. This way you are seeing everything, which is way more complicated than you probably need to see it.