Ok, is that a "think"/"belief" or something from a study?
Over the past few years I've read quite a bit of research on vitamin D. From what I recollect, the conversion process from source to final homone takes from 1 to 2 months. The beauty of our site is that the information exists for all to see. I suggest you visit the jounals section
to read for yourself how our bodies conduct this process. Then you don't have to rely on my feeble memory. You can even correct me too if necessary.
I recommend you start with Vieth's research.