Timelines are not an out-of-the-box chart type in Tableau, but they can serve several practical purposes for your analyses and user experience. First, a timeline in Tableau can be used as a method for showing end users when notable events occurred in the business. For example, you can provide context by lining up a timeline of marketing promotions with a trend line to see when spikes align with your marketing efforts.
Second, a timeline can be used as a calendar showing upcoming dates of interest. In both use cases, you can use (1) a relative date filter in Tableau to dynamically display a subset of dates and (2) add dashboard actions to link to more information about notable events / dates on the timeline.
This tutorial shares how to make a timeline in Tableau and how to add an optional reference line to display the current day.