All UCs post-bac is a year long program starting at the beginning of summer. I believe each UC Post-Bac program has a specific type of students they are looking for: experience, extra-curricular, culture, etc.
I'm currently in the UCSF Post-Bac, so I can't tell you much about the UCD program. But I spoke to a couple of the students in the program last year and they said it was very helpful.