User blog comment:NASCARfan0001/Phineas and Ferb:Summer Belongs To You/@comment-406459-20100804030720

What I was trying to say was that, in my own personal opinion, Phineas and Ferb are always on a perpetual summer vacation, and the Christmas episode takes place after that. After all, remember what Candace said: "Sometimes we do things without knowing they're naughty. Sometimes, we do a whole summer's worth of them!" The "before school starts next year" line most likely refers to the fact that school won't be back in session until the beginning of January, which is technically a new year. (In the United States, the school year is usually September to June.)