While it can take millions of years for some sedimentary rocks to form, it's not a universal rule. The formation time depends on various factors like:

* Type of sediment: Some sediments form quickly (like sand) while others take longer (like clay).

* Climate: Weathering and erosion rates vary greatly depending on the climate.

* Geological activity: Earthquakes and tectonic movements can accelerate the process.

It's more accurate to say that sedimentary rock formation can take anywhere from a few years to millions of years.