I'm guessing (just guessing here) but he might do better with visual cues. Some things to try might be a kids calendar and a set of pictures on a velcro strip that can be rearranged for the day's activities, and visual reminders for whatever tasks need to be done. One child I cared for had a hard time remembering his tasks when he came home for preschool, so I made a Job Train out of cardstock, pictures of each job on their own car (cap and coat on one; toilet and hands w/ soap on one; lunchbox and schoolbag on one; etc.) with a pic of him as the "engineer". This worked really well--all I had to do was point out the pieces and ask him to "build the train".
You can also try singing the days of the week, but honestly, at this age, kids are still living in the present and so days of the week can feel abstract for some kids.
For what it's worth, I'm a preschool teacher and I see a LOT of parents sweating over what we call 'the basics'. I don't know if you are concerned about your child being prepared for kindergarten, but my feeling is this: let him go to preschool to learn how to trust other adults, to learn how to follow the transitions and cues of the group as they move through the day, and to practice their self-help and social skills. This is the foundation most kindergarten teachers need. They are very skilled in teaching shapes (which are tricky at times) and days of the week, etc. At this age, it is most important that children do much of their learning through play, so spending time enjoying shape and pattern blocks will be more pleasant than quizzing him for both of you--you can talk about the shapes as you work. It may be that the bar is being set a little too high for your little guy. He will likely learn all he needs to, and it may not be as fast as his peers, but I'm guessing that if an assessment doesn't show anything unusual, your son sounds like a pretty par-for-the-course kiddo to me!