I am unable to back date a newly created reading plan... This used to be a very useful trick to fix some of the limitations of the reading plan feature. I tried creating a 3 month plan starting yesterday... but no go.
[For example: If you wanted to have readings of 1 chapter a day in a book of 31 chapters, you could back date the readings to account for the title page, TOC, forward, etc.]
EDIT: I am running 5.2a Mac on OSX 10.9.2.