Paleotidal cycles ranging from semidiurnal to the lunar nodal cycle apparently are recorded by late Precambrian (∼650 Ma) rhythmically laminated sedimentary rocks (rhythmites) of postulated ebb‐tidal origin in South Australia. The rhythmites may provide unique information on paleotidal periods and Earth's paleorotation: the late Precambrian year contained in ∼13.1 (±0.5) lunar months and ∼400 (±20) days, and the late Precambrian lunar month ∼30.5 (±1.5) days; the periods of the lunar apsides and lunar nodal cycles were then 9.7 (±0.3) and 19.5 (±0.5) years respectively. These values suggest that since late Precambrian time the average equivalent phase lag [the angle between the Earth‐Moon axis and Earth's tidal bulge, derived from the response of the solid and ocean tides; Lambeck, 1980] was near 3° rather than the present value of 6°. Precambrian sedimentary rhythmites may record much valuable information on the early history of Earth's rotation and the lunar orbit.