I'm trying to figure out how Jon's day of birth fits in the timeline of the war, and assumed you wouldn't just tell me when he was exactly born.:-)
In his first chapter at the Wall, Jon reflects that his name day passed a fortnight before. I assume this was his 15th one. Dany's 14th name day was at the end of her chapter, on the far side of the Dothraki sea.
Now, if this was after Jon's chapter -- and (apparent) name day, it could be concluded, that Jon was born more than 1 year before Dany, and at least 3 months before Queen Rhaella left King's Landing.
I will spare you the rest of my speculations about the date of Jon's birth, since their only real conclusion is that Catelyn seems a little thick when she thinks that Ned fathered Jon as he returned 'Dawn' to Ashara Dayne.
Ah... I see what you're driving at here, I guess...
I will confess, the chronology of these books sometimes gives me fits. You would not believe how often I reshuffle the chapters, trying to find the one true perfect sequence. And then just when I have it exactly right, my editors weigh in from both sides of the Atlantic, each suggesting a slightly different chapter order.
It is always a balancing act, since I want the chapters to have a certain dramatic flow, I worry about certain storylines being forgotten if they are "off stage" too long, and there is a constant tug of war between character time and reader time (a character may have two chapters, taking place one day apart, but if two hundred pages of stuff about other characters separate those two chapters, the reader is going to perceive a long time as having passed, even if I begin the second chapter with, "When he woke up the very next morning..."
All of which is a long winded way of saying, no, Jon was not born "more than 1 year" before Dany... probably closer to eight or nine months or thereabouts.
I do intend to publish a timeline as an appendix in one or other of the later volumes, but even when I do, I am not certain I'm going to start detailing things down to months and days. With such a huge cast of characters, just keeping track of the =years= drives me half mad sometimes. Not to mention the colors of everybody's eyes.
As to your speculations about Catelyn and Ashara Dayne... sigh... needless to say, All Will Be Revealed in Good Time. I will give you this much, however; Ashara Dayne was not nailed to the floor in Starfall, as some of the fans who write me seem to assume. They have horses in Dorne too, you know. And boats (though not many of their own). As a matter of fact (a tiny tidbit from SOS), she was one of Princess Elia's lady companions in King's Landing, in the first few years after Elia married Rhaegar.
The rest I will save for the books.