Late September and early October is the time to re-seed and fertilize your lawns in the temperate zone. At this point, we have weeds, crab grass, holes from skunks and possums digging for grubs, chipmunk holes, wild strawberry infestations, and all sorts of other lawn miseries. (I do not have lawn irrigation - too much lawn to cover.)
Even though, in theory, we encourage minimizing lawn space (except for a good square for Croquet) and pleasant grass walking paths between gardens and borders, we do believe in pleasing, healthy lawn grass as a part of garden design.