IB analyst start date?

Hi all, just wondering when the typical start date is for incoming investment banking analysts is. I'm trying to plan a post graduation trip with some friends and need to know. I'll be working at MS/GS/JPM and will be in the 6 week (-ish) training program in NYC beginning in the summer for new analysts, but I don't know when the actual training start date is since it wasn't in my offer letter. When does training usually start?

Thanks!