Weekends between

Hi guys,

I'm trying to find out how many weekends there's between 2 dates and Googling I found this algorithm from
http://archives.postgresql.org/pgsql-sql/2002-06/msg00304.php

date := now - day_of_the_week
> interval := interval + day_of_the_week
> date := date + int( interval/5)x7 + ( interval mod 5)


Assuming that now is current datetime, what I should expect from a date - int? or some1 could explain it better please?