Labor Day, the first Monday of September, marks the end of summer for many people, even though fall doesn’t officially start until a few weeks later. After Labor Day weekend, pools close, boats dock and adults no longer wear white pants freely. After the final barbecue or parade, an almost somber feeling seems to join with the pre-fall air and create the unmistakable smell of responsibility. It’s back to school, back to campus, back to work. But take heart: Memorial Day weekend, the unofficial beginning of next summer, is just three seasons away.