3 months, but once the build date and things start to set in place the dealer can find out a delivery date. The delivery date will be a friday and they will tell you anytime that week typically... Mine came in the thursday of the week they predicted it to arrive.
If your dealer says they can't get you that info tell them to have their general Manager or as high up in that dealership to get it for you.
Mine was needed as I literally was bringing 5 miles away to the clear bra and tint place so I needed to be sure all ducks were lined up.
Good luck and enjoy your new Z.... Be sure to follow the engine break in procedure too