As winter continues in the Northern Hemisphere, the daily periods of sunlight continue to lengthen. Our 24-hour clock is based on the average length of a day with the solar days near the solstices longer than those near the equinoxes. For Washington, D.C. and similar latitudes (I’ve not checked for other areas) the latest sunrise of the year (ignoring Daylight Saving Time) occurred on January 4. Monday, January 13 (the day of the full Moon), morning twilight will begin at 6:24 a.m. EST, sunrise will be at 7:26 a.m., solar noon will be at 12:17 p.m. when the Sun will reach its maximum altitude of 29.8 degrees, sunset will be at 5:08 p.m., and evening twilight will end at 6:11 p.m. By Wednesday, February 12 (the day of the full Moon after next), morning twilight will begin at 6:04 a.m., sunrise will be at 7:03 a.m., solar noon will be at 12:23 p.m. when the Sun will reach its maximum altitude of 37.7 degrees, sunset will be at 5:43 p.m., and evening twilight will end at 6:41 p.m.
