Changing status from Pending to Confirmed changes date to 1970

Im having trouble when i change an appointment status from pending to confirmed. Everytime i do this the date gets automatically changed to 1 January 1970.

After some trial i discovered that the problem occours only when im using the full date in portuguese on my wordpress install, which is set as follows:
j \d\e F \d\e Y

That's the portuguese version for presenting the full date.

I tried in different websites and the error occured everytime i set the wordpress date to the portuguese version of it so its easy to replicate my issue.

Any hopes for a solution in future releases?

Thanks.