I believe that the first time they offered free dining in the winter was 2008. We arrived on November15 and left November 25 (Tuesday of Thanksgiving week) and had free dining. We went to Grandma's in Tampa for Thanksgiving, returning on Sunday, November 30 and stayed for 10 days again on free dining.
If I recall correctly, the entire week of Thanksgiving was not eligible for free dining IF YOU CHECKED IN AT THAT TIME....but if you check in during the free dining period you can get free dining for your entire stay (or was there a limit of 10 days?) even if it extended into the non-free period.
In other words, I think that our Sunday/Monday/Tuesday of Thanksgiving week was only free dining because we were there the Saturday before which was free dining period.
Hope that makes sense.
Since then they've had free dining in November/December, but each year the dates included have been different.
They announced that 2008 free dining the first week of August.....but since then they've done the announcements as early as June or July. And of course, this year, they announced it last spring for dates that extend into next year....again unprecedented dates for free dining.
I think Disney is realizing that the free dining is a huge draw for people.....and since their markup on the food is so high it's really not that a loss for them....they get rack rate for their hotel rooms, fill them thereby also filling the parks (with park admission that is rarely discounted), and filling their restaurants. Good marketing on their part for sure!
One caveat to consider in upping your child's age in Disney's records. We did that because my girls (twins) then 8 years old would not have been happy eating mac and cheese while I ate steak and salmon, so with Disney's permission we termed them adults, age 10....I bought adult tickets (though they had a term for it, I think it was "junior"), upgraded them later to adult/junior APs which was very little difference and we paid for the dining (this was before free dining in winter was offered). Sounds great.....but now fast forward 8 years and the girls are 16....but Disney's records show them as 18....remember we aged them 2 years. So, that means that next year we may be required to pay the extra adult in the room fee. My plan is to bring a copy of their birth certificates, and explain to them what we did, WITH THEIR PERMISSION, in fact, their suggestion on how to get them the adult dining....and hope that they correct their ages in the computer so that our trips for the next two years until they really do turn 18 won't include an extra $25 a night fee!
Either that, or I'm going to change my name, lol, so they don't have any record of us ever visiting WDW before and my 16 year olds can stay 16.