Time & Calendar
Advanced

Sidereal Day

Earth's rotation period measured against the stars, not the Sun.

Formula

Tsid=Tsol1+Tsol/TyrT_{sid} = \dfrac{T_{sol}}{1 + T_{sol}/T_{yr}}

Variables

T_{sol}Solar day (24 h)
T_{yr}Orbital year

Example

≈ 23 h 56 m 04 s

Did You Know?

A sidereal day is ~4 minutes shorter than a solar day because Earth must turn a little extra to face the Sun again.

siderealastronomyrotation