Time can very for different varieties and locations, even between locations that aren't that far apart.
My advice, for what it's worth, is to check them every so often and see if they are ready. I think the general guideline is to check the color of the lupulin inside, and to bend the cone and see how it bends back. Also some report a "papery" feel when they are ready. It's important to do the last two checks after the overnight moisture has gone away. So try checking in the afternoon.
Freshops.com has some growing advice and there are more out there as well.
FYI the bines will kind of scratch you when you harvesting and it can make your skin itch a bit. Also, the resin from the flowers will stick to your fingers, even after washing, so be careful abotu touching your eyes and licking your fingers (It will sting your eyes and make your fingers taste very bitter...)