iPhone 6S / 6S Plus: announced 2015-09-09, pre-orders begun 2015-09-12, released 2015-09-25
iPhone SE: announced 2016-03-21, released 2016-03-31
Don’t mess with the bull, son, you’ll get the horns.
EDIT: seems I changed the order just after posting, and put the SE after the 7 rather than before. Still shouldn’t be before the 6 though!