How a Sundial Tells Time

A sundial in Beijing tells time by the Sun's apparent position.

The earliest known sundials are shadow clocks from 1500 BC Egypt.

A horizontal sundial in Melbourne has a flat plate and gnomon.

Two wires on a bifilar sundial cast shadows indicating date and time.

An equatorial sundial in Karlsruhe aligns its style with Earth's axis.

A Perth sundial works properly at latitude thirty two degrees south.

Hour lines on a thyme garden sundial indicate the time of day.

A Singapore Botanic Gardens sundial shows time by horizontal shadow.

A Sunquest sundial requires 3 corrections for national clock time.

Earth's orbit causes differences up to 16 minutes, 33 seconds.

A Kew Gardens sundial needs longitude correction for official time.

Daylight saving time usually demands an extra 1 hour shift.