I found this site on the net which gives your info, http://www.cookeryonline.com/Game/Preparing%20Game.htm

Stu

Hi tdbuya,  Older birds need to be hung for a few days to tenderise the flesh
but if they are still young they can be cooked after a day or so.  They should be fast roasted and it is best to cover the breast with unsmoked streaky bacon and secure with string.  Preheat oven on gas 7 or elec.220c and roast for 20mins.per 450g.  [If it is a cock bird it will need to be hung longer as they can be toughr than the hen.]  Bread sauce is great with pheasant.  Make as follows:  Bring 600mls milk slowly to the boil with 1 bayleaf and a small
             onion studded with 6 cloves. Remove from the heat and leave
             to stand for 30mins. Whisk in 125g soft white breadcrumbs and
             simmer, stirring regularly, for 15 mins.  Remove onion and
             bayleaf, and beat in 25g butter. add salt and pepper and a little
             nutmeg. 
I used to cook pheasant regularly when I lived in the u.k. but in Malta I have never been able to get any.  Enjoy it

Well, the pheasant hunting season in u.k starts August 12th,therefore I assume it might be about 8.months old.  As these are bred solely for this purpose I would reckon this would be called old, as they start breeding again in the spring. I'm no expert but it seems to make sense on this logic.  So give it four-five days as its in a nice cold shed