Date operations.

Hi All, I have a problem working out a suitable algorithm either in PHP or MySQL. Basically I have a DB that keeps track of breeding records. Each record has a paired data, and a split-up date. I need to generate some statistics to work out average numbers of pairs per month, averaged on a daily basis, for a given start and stop date, typically a year or year-to-date. All the algorithms I can think of are messy, where I have to loop through all the breeding records for every day of the year, and count how many pairs are breeding by seeing if the date is between the start and stop dates, and then average that on a monthly basis. I can't see that scaling very well, as there might be several hundred breeding records for a given year, multiplied by 365 days. Has anyone any hints/pointers for an efficient way to do this? Regards, Garry.