I recieved my tickets today for Green Day which is in October
At the same time, however, I have yet to recieve my tickets for The Gossip which is at the end of the month.
When you get your tickets varies on the size of the event and how badly the tickets are likely to be touted. Green Day is one such event which is why I was surprised at how early they arrived. However, for music festivals such as T in the Park and Glastonbury, where people are likely to have bought the tickets purely to sell on to make a profit, they don't arrive until much closer to the date.
Each year, I recieve my T tickets just a few days before the festival and I'm sure MJ will be the same. I think all tickets will be sent out late June, and opening night tickets will be with you for 2nd/3rd July-ish.