Field help:
Start of production
Enter the start date of the initial construction of the building.
For buildings requiring approval, this is usually the date of the first building application. It is not the date of completion or occupancy.
If the exact date is not known: For buildings constructed before 2010, you can enter 01.01. of the construction year.
Example: The house was built in 1998, the exact date of the building application is not known. Enter 01.01.1998.