CakePHP Model with "Between dates"

I have a large data set (over a billion rows). The data is partitioned in the database by date. As such, my query tool MUST specify an SQL between clause on every query, or it will have to scan every partition.. and well, it'll timeout before it ever comes back.

So.. my question is, the field in the database thats partitioned is a date..

Using CakePHP, how can I specify "between" dates in my form?

I was thinking about doing "start_date" and "end_date" in the form itself, but this may bring me two a second question.. how do I validate that in a model which is linked to a table?