Day of the Week- multiple rows!???

Hello,

I am working in a Excel file and need help! I do not know a whole lot about excel so this should be interesting.

I have a file where clients each have their own row and each column represents a different piece of information about the client, ie. name, phone number, address, etc. One of the columns represents dates. I created another column that will then show the day of the week for that date. I have learned how to apply the day of the week function. The problem I am running into is that I have 200+ clients, all with different dates. Typing the function into each row will take forever, and i would assume there is an easier way to do this.

The dates are in column J and the Day of the week column K.

Is there a way to make the date in 13 J the day of the week in 13 K, the date in 14 J the dat of the week in 14 K, etc. all at the same time...?

Sorry if I am not making sense, I don't really understand this.

Any help would be appreciated!