User blog comment:SayuriDarling/The Demigod Diaries Official Discussion Blog/@comment-4515675-20120815183719/@comment-4515675-20120815193617

But this is not just a small mistake, think about it. There's no way this can all make sense. When they were on their quest in TLH it was clearly winter, it's mentioned every few pages how it's cold outside and it's snowing. Then Leo says two months have passed so it should be February but it's Christmas Eve instead. Not to mention how it would be very hard to explain how Jason and Piper got together exactly two days after their quest ended.

In SoN the fans could come with different explanations like how Percy was just confused about the time he spent sleeping and how Jason could have been taken by Hera in Sept and kept two months somewhere. However, the inconsistency in the DD can not be explained by anything, again he has editors who should point out these things to him.

I don't know, maybe it's not important since the DD is technically an extra book but as long as he gave info that is vital for the rest of the books from HoO I think he knew or at least expected most of his fans to read it.