Click on Send to Mail Recipient from the Quick Access Toolbar. In the Email dialogue box, select the option 'Send the entire workbook as an attachment'. Click OK. This will open an outbound email with the workbook attached to it. Click on Send.

This is an option in Excel via the following path:

"Home" tab -> "Number" section -> type dropdown -> "More Number Formats" (at the very bottom) -> "Custom"

Once there, you can make your own custom format by simply typing in "dd-mm-yyy" and apply it to whatever cells you want.

Custom Formatting box

*Edit: It's unclear what exactly you're asking. The question would benefit from some more context about what you're looking to solve.