If anything, I believe the date for the coup on Thanedd to be wrong. If I remember correctly Geralt, Dandelion and Milva set of from Brokilon in June, after Geralt had been there for 5 months, which means the coup on Thanedd happened in Jan/Feb. But if the coup happened that early in 1264, it means that Ciri barely spent a year in Kaer Morhen and Ellander combined.
My impression is that Ciri had been at Kaer Morhen for some time when Triss arrived. And Triss stayed the winter and they left in spring for Ellander. So, Ciri was probably in Kaer Morhen for a year. And then she was in Ellander with Yennefer for about a year as well, if we say she arrived there in Mar/Apr and left for Thanedd with Yen i Jan/Feb the following year.
So, Ciri was with Geralt and Yen for about two years before Thanedd. But, even if the massacre of Cintra was in early 1262, it doesn't add up. Because, she was on the run for 7 months afterwards, and then 2 years with Geralt and Yen, and the coup on Thanedd happened Jan/Feb. So, the coup must have been in 1265 instead I think. Although, it can be possible that she arrived at Kaer Morhen around August of 1262, and left in spring of 1263, and then spent almost a full year in Ellander. But, that's an awfully short time for her to learn all of her Witcheress skills.
And then we have all the events after Thanedd. If my theories are correct, and Thanedd happened in Jan/Feb and Geralt left Brokilon five months later, then where did all the years go before 1268? Geralt and co. leave Toussaint in January the following year after Thanedd, and the impression I got was that they went straight to Castle Stygga to rescue Yennefer. So, where talking about early 1266 when the events at Stygga happens. I guess it is possible that Geralt, Ciri and Yennefer travels the world for two years to all the places where Ciri was in, before August of 1268 when the pogrom of Rivia happens. These dates would also mean that Ciri spent about a year on her own, down in the south with The Rats, Bonhart and Vysogota, which I believe sounds about right.
But, there are still some inconsistencies. If my years are correct, then Ciri was at Vysogota's in October and a couple of months ahead, of 1265. But, Vysogota mentions she is not nearly 16 at the time. Which, she wasn't. She would have just been 14 then. But, when Sapkowski writes she was not nearly 16 then I take it to mean she was 15 going on 16, but she could of course have been 14.
And another thing that confuses is that the chapter about Battle of Brenna is before the chapter about Stygga, even though through my calculations in this post the battle took place two years later after the events at Stygga.
Just some thoughts. The timeline of the books always had me scratching my head a little...
---------- Updated at 04:23 PM ----------
Just noticed that the wiki says Nilfgaard invades the North in July of 1262, which means that the massacre of Cintra took place at the same time. So, add those 7 months when Ciri was on the run after the massacre and we get that Geralt finds her in, like, January 1263. So, Ciri is in Kaer Morhen until spring of 1264, when she leaves for Ellander. And as I discussed above, Geralt and co. leaves Brokilon in June, after Geralt has spent 5 months there after Thanedd, which means that the coup on Thanedd took place in about February that year. But, since Ciri went to Ellander in the spring of 1264, the coup on Thanedd must have happened in 1265, just as I guessed in the post above. Progress!