The main parts of a sundial are an erect stylus and a calibrated disk .As the sun moves in the sky, the shadow of the stylus moves like a clock hand around the disk indicating the hours.

• 日晷的主要部件是由一根晷针和刻有刻线的晷面组成，随着太阳在天空运行，晷针的投影像钟表指针一样在晷面上移动，就可以指示时辰。