I am assuming travel_date is a date datatype column.
Following are the steps to apply database function on a column :
1) click on the selection
2) “More” option will come and click on "More" option
3) In more option, you can apply any of the database function
4) The list of database function is displayed based on column datatype.
5) Then, select the function ( in your case quarter, month, day can be selected )
To apply single database funtion, please refer to the link "Quick Database Function"
5) To apply nested function, refer to the link "Advanced Database Function"
Helical Insight Team