Here are four ways to express dates using data validation: literal values, input values, a list, and formulas. I’m using Excel 2016 (desktop) on a Windows 10 64-bit system.

By combining Excel’s GROUPBY function with dynamic formulas, data validation lists, and conditional formatting, you can create an interactive data summary with robust drill-down capabilities.

Data Validation in Microsoft Excel allows users to control the type of data entered into the worksheet. It picks from a list of rules to limit the type of data that can be entered into a cell.

Figure A We’ll add a data validation control to this sheet. Click the Data tab, and then, click Data Validation in the Data Tools group. In the resulting dialog, choose List from the Allow dropdown.