You can select/unselect the use of the time field for the transformation by clicking on the check box in the top left corner of the panel (only available during the transformation definition step).

If the use of the time field is selected, select the time format in the combo box.

If you select "User defined pattern", enter the pattern on the corresponding text field, by following these rules: For example, a time pattern can be [YYYY]-[MM]-[DD]T[hh]:[mm]:[ss].
The following format is also accepted (no separator): [YYYY] [MM] [DD] [hh] [mm] [ss].