WASHINGTON (AP) - A sharp drop in auto sales caused largely by a calendar quirk lowered U.S. retail spending in September. But Americans boosted their spending on most other goods, suggesting confidence in the economy ahead of the government shutdown. The Commerce Department says retail sales dipped 0.1 percent, the weakest showing since March. Auto sales fell 2.2 percent, the largest decline since October 2012. But the drop was largely because the sales calendar pulled Labor Day weekend activity into August, the automakers have said. That means the drop is likely temporary. Excluding autos, gas and building supplies, sales rose 0.5 percent in September, up from 0.2 percent in August and the same as July's figure. Economists exclude those categories to get a better sense of consumer demand.