Answer

1. In Tableau Desktop, connect to a live data source.
2. In the Data pane, right-click the data source name and select Extract Data.
3. Under the Filters (Optional) section, click Add....
4. Select the date field that will be used for filtering.
5. Click OK.
6. Select Relative date and click Next.
7. Set Relative date to Days and select Today.
8. Click OK.
9. Under Number of Rows, select the Incremental Refresh check box.
10. From the Identify new rows using column drop-down menu, select the date field from Step 4. 
11. Click Extract.

Additional Information

• The filter in the extract handles the initial extract and the incremental extract set to the date field will add new data to the extract based on the date.
• May be necessary to add a filter to the view that will filter the data in the view to only today as well.