On May 15 Greece has to “roll over” €1.4B in debt, which means sell more debt to pay debt, or borrow money to pay money back. They can do that because the banks keep buying more T-Bills. What they can’t do is pay the IMF anymore. €305M on June 5. €343 a week later. There is no more money left in the IMF monopoly account at the IMF to pay the IMF back with. There’s nothing left.
It looks like it’s June 5th.
The Jewish Libertarian 
I’m betting trouble or trouble starting on June 6th. so before 6th probably nothing happens, so I bet Greek default on June 12th not 5th. They can still stir it on the 5th. 😛 Hot summer.