Explanation
Data validation rules are triggered when a user adds or changes a cell value.
This custom validation formula uses the WEEKDAY function to get a numeric value, 1-7, corresponding to a week beginning Monday (1) and ending Sunday (7). To get a number for a Monday-based week, the return_type argument for WEEKDAY is provided as 2.
The WEEKDAY result is then compared to 6. Any value less than 6 is a weekday, so the expression returns TRUE and validation succeeds. If the weekday number is not less than 6, validation fails because the date is a Saturday or Sunday.
Date is weekend
To allow only dates that occur on a weekend (Saturday or Sunday), you can use a similar formula:
=WEEKDAY(C5,2)>5
Note: Cell references in data validation formulas are relative to the upper left cell in the range selected when the validation rule is defined, in this case, C5.
Data Validation Guide | Data Validation Formulas | Dependent Dropdown Lists
Explanation
Data validation rules are triggered when a user adds or changes a cell value.
The TODAY function returns today’s date (recalculated an on on-going basis). The AND function takes multiple logical expressions and returns TRUE only when all expressions return TRUE. In this case, we need to test two conditions:
The first condition checks that the input is greater than today:
C5>TODAY()
The second condition checks that the input is less than today + 30:
C5<=(TODAY()+30)
(Dates are just serial numbers in Excel, so we can simply add 30).
If both logical expressions return TRUE, the AND function returns TRUE and validation succeeds. If either expressions returns FALSE, data validation fails.
Note: Cell references in data validation formulas are relative to the upper left cell in the range selected when the validation rule is defined, in this case C5.
Data Validation Guide | Data Validation Formulas | Dependent Dropdown Lists
