It’s just like new construction, meaning that your house will show as built in the present year you start building. The only thing is that the process of doing it will take months and month sometime more then a year depend on the area the land is located. There are ways to make it faster if you leave rooms or even 1 wall, so it won’t count as new construction but your year built will be same as now. Hope I helped you.
P.S. Built new construction is much more value in resale price 