Time: UTC, local time and daylight

Time begins with the Sun. Apparent (solar) time is what a sundial shows: noon, the Local Apparent Noon, is the instant the Sun crosses your meridian and a vertical pole's shadow points due north or south. The Sun appears to circle the Earth once a day, 360° in 24 hours, so it moves 15° of longitude per hour. Hold on to that number; it links time and longitude throughout this subject.