A sundial's shadow points roughly north at local noon in the Northern Hemisphere.

The longer version

For observers in most of the Northern Hemisphere, the Sun stands due south at local noon, so any shadow falls toward the north. A dial set up correctly will therefore show its shortest shadow of the day pointing along the north-south line. The shadow is also at its shortest then, since the Sun is highest.

That moment is not what a clock reads at twelve, because time zones average solar time over a wide band and daylight saving adds another hour. The gap between sundial noon and clock noon can be substantial, which surprises people who assume the two should agree. Longitude within the zone explains most of the difference.

Where this entry sits

These facts wander through clocks, calendars, time zones, and the long human effort to measure passing hours. You will find leap years, odd month lengths, ancient sundials, and the reasons modern timekeeping works the way it does. The full list sits on the Time and Calendars page, where every entry is listed in order.