The New Cosmos. An Introduction To Astronomy and ...
We define: one Julian century= 36 525.0 d siderial year= 365.25637 mean solar days. as the time between two passages of the Sun through with 1 d = 24 · 60 · 60 s = 86 400 s has been defined. the same point in the sky (from sidus ="star"); it is thus the true orbital period of the Earth. One The Measurement of Time.
