Developer information varies. What is the realistic construction time?

Hello,
with some developers you hear that the houses are built within 3 months, with others it takes 6 months.
Which construction time is really realistic?

3 months is unrealistic, 6 months as well.
Rather calculate with 9 (to 12 months). Then you are on the safe side.
We are indeed building with an architect, but we started at the beginning of September and will move in at the end of May, and we hardly had any waiting times between the trades, and it wasn't really a proper winter anyway. And a basement didn't have to be built either.

On a slab foundation and in favorable weather, 6 months are feasible, of course not with a basement...

Our current house was built in 4 months.

So a neighbor of ours built his house himself with companies from April to October 2014. (He took half a year of parental leave for this.) A 200 sqm Frisian house plus approx. 130 sqm garage with a gable roof.

From purchase to moving in, 9 months is realistic, but due to the current workload of construction companies, it is not possible everywhere. It can be faster, but it becomes stressful for everyone involved. There are also differences in construction types and whether it is an architect, developer, or general contractor. A building permit or building notification also makes a time difference.

The 3-month construction period is correct, but no one tells you when they start. For some companies, the construction time is extended again in the finishing phase. "Oh, you want underfloor heating? Then it takes 3 weeks longer..."
If you plan including planning and buffer for 9-12 months, it will usually fit.