Opening a Timeline view plots data of all descendants that have a $StartDate defined. For instance, if a container has child containers - without dates set - titled to represent years, and these contain notes with $StartDates then the view will show the events for all years whilst the year containers will be listed in the 'No Date' sidebar. This is a powerful feature as the non-plotted year containers can help with data/note management without affecting the actual timeline visualisation.
It is not possible to define any other attribute than $StartDate as the inclusion criteria for the timeline, or to use numerical or other sequence data (as opposed to Date-type data). Note: Until v5.9.3, if no notes in the container had a $StartDate, Tinderbox used $Modified instead; this alternate option was discontinued after v5.9.3.
Items without dates are placed in a "No Date" column at the side of the view.
Remember Tinderbox's built-in prototypes as these include an Event prototype that is ideal for timeline data items.
By default, the timeline will encompass all dates in scope but it is possible to set $TimelineStart and/or $TimelineEnd in the container note to set a specific duration within which data is displayed. If these boundaries are set, outlier data is placed in a "Out of Range" column at the left side of the view (and to the right of a 'No Date' column, if present).
Dates with an $EndDate only or where $EndDate is before $StartDate will plot, but incorrectly - such configurations are effectively invalid.