This example illustrates how you can apply functions to derive day-of-week values out of a column of Datetime type:

• WEEKDAY - returns numeric value for the day of the week for source Datetime values. See WEEKDAY Function. 
• WEEKNUM - returns the numeric value for the week within the year for source Datetime values. See WEEKNUM Function.
• DATEFORMAT - can be used to format Datetime values in many different ways. See DATEFORMAT Function.

Source:

Transformation:

The following transformation step generates a numeric value for the day of week in a new column:

The following step generates a full text version of the name of the day of the week:

The following step generates a three-letter abbreviation for the name of the day of the week:

The following step generates the numeric value of the week within the year:

Results: