If you need to get the day name (i.e. Monday, Tuesday, etc.) from a date, there are several options depending on your needs.
Do you just want to display the day name?
If you only want to display a day name, you don't...

To generate a dynamic series of dates that are weekends only (Saturday and Sunday), you can use the WORKDAY.INTL function. In the example shown, the date in B5 is a hardcoded start date. The formula in B6 is:
=WORKDAY...

To calculate work hours between two dates with a custom schedule, you can use a formula based on the WEEKDAY and SUMPRODUCT functions, with help from ROW, INDIRECT, and MID. In the example shown, the formula in F8 is...

If you want to use conditional formatting to highlight dates occur on weekends (i.e. Saturday or Sunday), you can use a simple formula based on the WEEKDAY function.
For example, if you have dates in the range C4:C10...

To get the nth day of week in a month (i.e. the first Tuesday, third Tuesday, forth Thursday, etc.) you can use a formula based on the DAY and WEEKDAY functions. In the example shown, the formula in E5 is:
=B5-DAY(B5...

To count dates by weekday (i.e. count Mondays, Tuesdays, Wednesdays, etc.), you can use the SUMPRODUCT function together with the WEEKDAY function. In the example shown, the formula in F4 is:
=SUMPRODUCT(--(WEEKDAY(...

To build a Gantt chart with weekends shaded, you can use Conditional Formatting with a formula based on the weekday function.In the example shown, the formula applied the calendar, starting at D4, is:
=WEEKDAY(D$4,2)...

To count weekdays (Mondays, Fridays, Sundays, etc.) between two dates you can use an array formula that uses several functions: SUMPRODUCT, WEEKDAY, ROW, and INDIRECT. In the example shown, the formula in cell E6 is
=...

To get the last working day in a month, you can use the WORKDAY function together with the EOMONTH function. In the example, the formula in C4 is:
=WORKDAY(EOMONTH(B4,0)+1,-1)
How this formula works
Working from the...

To check if a date is within the last n weeks of today's date, you can use a formula based on the AND, TODAY, and WEEKDAY functions. In the example shown, we are testing for dates in the last 2 weeks. The formula in...

To sum data by weekday (i.e. sum by Mondays, Tuesdays, Wednesdays, etc.), you can use the SUMPRODUCT function together with the WEEKDAY function.
In the example shown, the formula in H4 is:
=SUMPRODUCT((WEEKDAY(dates...

To check the weekday of a date, and roll back to Friday when the date is a Monday, you can use the IF and WEEKDAY functions. In the example shown, the formula in C5 is
=IF(WEEKDAY(B5)=2,B5-3,B5)
How this formula...

To get the Monday of the week (i.e. the beginning of a week) for any given date, you can use the a formula based on the WEEKDAY function. In the example shown, the formula in C6 is:
=B5-WEEKDAY(B5,3)
Note: In Excel's...

To get the last weekday in a month (i.e. the last Saturday, the last Friday, the last Monday, etc) you can use a formula based on the EOMONTH and WEEKDAY functions.
In the example shown, the formula in D5 is:
=...

To generate a dynamic series of dates that are workdays only (i.e. Monday through Friday), you can use the WORKDAY function. In the example shown, the formula in B6 is:
=WORKDAY(B5,1,holidays)
where holidays is the...