Expressing times

Numeric-only date format

If you must express a date in numerical date format, use the format YYYY-MM-DD, and separate the elements by using hyphens. This conforms to ISO 8601 international standards for numerical date format.
Additionally, if you have a choice of what date to write (such as in a fictional example), then choose a calendar day greater than 12 to differentiate it from the month.
Recommended: 2017-04-15
Not recommended: 04/06/2017

Expressing divisions of the year

Avoid referring to seasons. Spring in the northern hemisphere is fall (autumn) in the southern hemisphere. Instead, use the month, quarter, or temperature (if relevant).
For cube data sources, dates dimensions are usually organized into hierarchies that contain levels such as year, quarter, and month. In addition, some multidimensional data sources have time intelligence enabled, which makes it possible to look at data levels different ways, such as Months by Year, Months by Quarter, Weekends, etc. These levels are represented as attributes of the hierarchy. Hierarchies and attributes are defined when the cube is created and you cannot modify them in Tableau. For example, the Year dimension from an Oracle Essbase data source is shown below.
When you place a multidimensional date on a shelf, the field is treated like any other dimension. For example, you can drill down, drill up, and so on.

Dates in Relational Data Sources

For relational data sources, dates and times are automatically placed in the Dimensions area of the Data pane and are identified by the date  or date-time  icon. For example, the Order Date and Ship Date dimensions from an Excel data source are shown below.
When you place a relational date on a shelf, the field name is automatically modified to reflect the default date level. Tableau defines the default date level to be the level at which there are multiple instances. For example, if the date field includes multiple years, the default level is year. However, if the date field contains data for just one year but includes multiple months, then the default level is month.
If you don’t want Tableau to automatically select a date level and would rather have a date dimension be a continuous field, you can right-click (control-click on Mac) the field in the Data pane and select Convert to Continuous. The dimension then turns green in the Data pane; now when you use that dimension in a view, it will be continuous. You can easily revert back by selecting Convert to Discrete from the field’s context menu in the Data pane. You can also convert a field in the view to continuous while it is on a shelf by selecting Continuous on its context menu (which you can see when you right-click (control-click on Mac) the field). The field on the shelf turns green but the field in the Data pane is still discrete.