ESPP, check your company policy

Typically ESPP is calculated in 6 month period, but your company has a 12 month investment window. The purchase price, typically, is the lowest closing date either at the start or end of the purchasing window. In your case, it should be the lower of May 31 of 09 or June 1st of 10. You take the 15% discount at either that date. Here is the trick part, some companies imposing block out date after purchasing, that is force you to hold after the stock is purchased. Check w/ your company HR for this, and this should be the only reason to lose money on ESPP plan.