Additionally the date is not exact because that would depend on the dureation you want of the script and what is the idea. Simple ideas like a romance or action can be done in less than a day or one day, however other ideas like historical, biblical, scientific requires research.
All in all it is expanded idea or simple ones can all be done very nicely. It is a hobby of mine since I was a child to write screen plays for theater and movies (I'm a writer, director myself), professionaly speaking not plain scrapt scripts for children I'm talking professional. using final draft.