Get Day Name From Date

TEXT(B4,"ddd"): 

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?

"ddd"  // "Wed"
"dddd" // "Wednesday"

Excel will display only the day name, but it will leave the date value intact.

Do you want to convert the date into a day name?

If you want to convert the date value to a text value, you can use the TEXT function with a custom number format like "ddd". The formula looks like this:

=TEXT(B4,"DDD")

The TEXT function converts values to text using the number format that you provide. Note that date is lost in the conversion, only the text for the day name remains.