Actually I don't know you've noticed or not, an attempt in the time trial events of those seasonals doesn't count for a day. I was hoping to enter that one to refresh me some new UCDs but there was nothing new showed up.
For some reason, PD removed the days system from GT4 & earlier -- I liked the system. Now, to recognize a day passing is when you see a loading bar before you enter onto a track. That counts a day passing & a 6-car update in the UCD. This is then recorded right onto the save.
Not sure why PD would include this other than the importance of the UCD's update cycle..