Data Validation to Ensure a Weekend Date
If you want to ensure the user enters a date that is a Saturday or a Sunday, you can use a Custom Data Validation.
This example is for cell A1.
To open the Data Validation dialog use Alt a v v (pressed in sequence, not held down).
Click the first drop down and select Custom. This allows you to enter a formula to determine the data validation.
The formula used is
The WEEKDAY function returns a number from 1 to 7 for the days of the week. The ,2 in the function means 1 = Monday, 6 = Saturday and 7 = Sunday.
Click OK to apply.
If you wanted to ensure weekday dates you could use the formula