How can this be changed?

If I put in a cell, which is formatted with standard number, a number input that is separated by an underscore, is there after giving a carriage return, a date of created. How can this be changed?
Martin

Except you have set up in: Menu/Tools/Options/Language settings - Date acceptance patterns one with “_” underscore as separator, or is default separator for the language in locale settings, I don’t know how it can be converter in a date.