Use the function =NOW(). It returns both date and time, which update when the file is opened or recalculated.

This is ideal for automatic logs in reports. But if you need to fix the moment of creation, the formula won't work — use Ctrl+; for date and Ctrl+Shift+; for time.

To change the format, select the cell and press Ctrl+1. For more on which Excel hotkeys save hours of work, see the guide.

🔗 Source: excel.rf