list organization question

[Robocop]

I'm currently trying something along the lines of a sort.compare, but
as i'm never sure how many mini-lists i'll end up with, i'm not sure
how exactly to begin.  Maybe something like a C vector, i.e. a list of
pointers to other lists?  Or more specifically, compare dates in my
list, push that into some empty dates[], then do something along the
lines of for looping over dates to create subset lists, and nesting
some more compares within these lists to further sort the data by id.
Sound crazy or plausible?