The utility model provides an equatorial sundial. The equatorial sundial comprises a
latitude plate, a sundial surface fixing plate, a sundial disc and a
time difference speed checking ruler, the sundial surface fixing plate is formed by folding a sundial surface fixing plate front surface and a sundial surface fixing plate back surface, geographic
longitude scales are arranged on the sundial surface fixing plate front surface, and the sundial surface fixing plate is fixed on one side edge of each of the two
latitude plates; the sundial disc is clamped between the sundial surface fixing plate front side and the sundial surface fixing plate back side of the sundial surface fixing plate, a sundial needle is arranged in the center of the sundial disc, time scales are arranged on the front side and the back side of the sundial disc, and the front side of the sundial disc is further provided with a geographic
longitude alignment line, date scales and a true ordinary
time difference graph corresponding to the date scales. The geographical
longitude alignment line is aligned with the geographical longitude of the corresponding observation place on the geographical longitude scale; one end of the
time difference speed checking ruler is provided with a first positioning hole which can be positioned on the sundial needle, and the time difference speed checking ruler is provided with time difference scales. The time difference measuring device can be widely applied to different places, and is convenient to measure time difference and convenient to manufacture.