Can't format hardkey date data as a date in Google sheets?

I've got some date data in a Google drive sheet which is imported from a CSV.

The date data is formatted as either dd/mm/yy or dd.mm.yy as hard key data (eg. not formatted as a date)

I got to format > number > date but it doesn't work.

Any idea how I can format these as dates in Google sheets ?

I've made an example spreadsheet here: https://docs.google.com/spreadsheets/d/1FyU526G55dVwKDryaNS1Dz_U2XZpIa9chDCJDcRxQzg/edit#gid=0