How do I correct date format?

Just downloaded bank statement in .csv format.

When I load it into Excel the date column contains a number, 7011.
When I try to convert this to something more meaningful, Format > Cell
> Date and select my prefered format it comes back as 12/03/1919, when it should be 20/05/2006.

Any suggestions as to how to fix this?

Ooops!

Operator error please ignore earlier posting.