Input type DateTime - Value format

Question

In which format should I put the date and time, for use in the HTML5 input element with the DateTime type?

I have tried:

• 1338575502
• 01/06/2012 19:31
• 01/06/2012 19:21:00
• 2012-06-01
• 2012-06-01 19:31
• 2012-06-01 19:31:00

None of them seem to work.