Rosemary

Definitely not at the end of the season. Best time is after flowering and, if it needs more, not later than mid/end August, depending on where you live.

I find that the lovely shrub Rosmarinus, is usually best clipped back (moderately) after flowering, leaving the rest of summer for the plant to rejuvenate. It is also the best time to take cuttings, so you achieve two goals for the price of one!
(Keir).

And don't cut into the old wood either