sunrise sunset

Astronomically, sunrise occurs for only an instant: the moment at which the upper limb of the Sun appears tangent to the horizon.However, the term sunrise commonly refers to periods of time both before and after this point:

The timing of sunrise varies throughout the year and is also affected by the viewer’s longitude and latitude, altitude, and time zone. These changes are driven by the axial tilt of Earth, daily rotation of the Earth, the planet’s movement in its annual elliptical orbit around the Sun, and the Earth and Moon’s paired revolutions around each other. The analemma can be used to make approximate predictions of the time of sunrise.