def every_sunday(d1, d2) one_day = d1.is_a?(Time) ? 60*60*24 : 1 sunday = d1 + ((7-d1.wday) % 7) * one_day while sunday < d2 yield sunday sunday += one_day * 7 end end def print_every_sunday(d1, d2) every_sunday(d1, d2) { |sunday| puts sunday.strftime("%x")} end print_every_sunday(Time.local(2006, 1, 1), Time.local(2006, 2, 4))