In Tableau, once a field is identified as a date, Tableau automatically creates a date hierarchy. The date field will allow you to drill down from year to quarter, to month, to day.

Dates can also either be discrete or continuous. With our Superstore dataset, lets drag our Order Date field to the Columns shelf. By default, when you drag a date over to either your column or row shelf, you will get a year, date field, blue pill. A blue pill means a date field is discrete. Which means, distinct values and this will produce a header for us.