I had my greenhouse built in 2001, it was started in May.
Florian had the greenhouse itself up within a couple of days and then getting the new heating and cooling system into the house, with ductwork through the garage with registers pulled into the greenhouse, that took forever. Then came the almost useless electrician and then getting the deck built, which required several revisions from the architect and town permits. All of this with plenty of town inspections!
I finally started to move my plants inside on 9/11, but construction was completed in the beginning of September. Due to the horrific attack we had the afternoon off from work.
So this whole construction really stretched out over almost four months, but it sure was worth it. It still looks great and it is super functional.