I usually pick mine about mid September. You need to watch for when they come off the tree without yanking but aren't fully soft. It can be a bit difficult because pears need to be picked before they are fully ripe and then brought into the warmth of the house to finish. Can't give an exact date of course because it depends on the type of summer we have had. At least it was better this year than the last 2. Another indicator I use is to pick them about 3 or 4 weeks before my Cox's or Grannies apples are ready. Not much of a help for you if you don't have a Cox or similar though.