Incorrect Member since date when Date Input Field is set to dd/mm/yyyy

I had this problem on my site (3.4.1) but also repeated it on your demo site.

Seems to be an issue with how the the Member since date is stored when using dd/mm/yyyy for the "Date Input Fields" .

No idea if it goes beyond CiviMember or is just limited to this.

So set "Date Input Fields" to dd/mm/yyyy

Create a new membership

Membership: Inner City Arts, student, individual

Member since: 21/05/2011
Start: 21/05/2011
End: 21/05/2012

Save and everything is ok

Now edit and the Member since date has the wrong date.

Member since: 01/01/1970 <- wrong date

Start: 21/05/2011

End: 21/05/2012

So edit the Member since date to 21/05/2011 and save

Error: "Start date must be the same or later than Member since."

Start date is now shown as 05/21/2011

Cancel, then change date format back to mm/dd/yyyy, edit to correct date and everything works again.