Moshe Pelberg of Baltimore wonders why, for a few weeks around the summer solstice (June 21), sunset and sunrise times both get later each day. "The reverse happens for three weeks in December," he writes. "Any idea why?" Too arcane for 87 words, Moshe. You can blame daily and seasonal variations in the Earth's orbit and spin, which stretch differences between "solar" time and "clock" time. Baltimore's sunrises will creep later after Friday, the year's earliest at 5:39 a.m. Our latest sunset is 8:37 p.m. June 27.