orbital

This web page shows that the orbital periods of Mercury, Venus, and Mars (expressed in Earth days) are - respectively - 87.9692 and 224.70067 and 686.9782

Earth's orbital period is The Sidereal Year, which is 365.25636 Earth days. This is confirmed by the image below, which is a scan from Schultz, Movement and Rhythms of The Stars, published by Floris Books, Edinburgh, 1986, Page 217, Table 2.2)

The image below is a scan from Schultz, Movement and Rhythms of The Stars, published by Floris Books, Edinburgh, 1986, Page 222, Table 4.5) It shows that the synodic revolution periods of Mercury, Venus, and Mars (expressed in Earth days) are - respectively - Mercury 115.8774 and Venus 583.9205 and Mars 779.9382

Mercury’s orbital period =

1 ÷ [(1 ÷ 365.25636) + (1 ÷ 115.8774)] = 87.9692 Earth days.  

Venus’ orbital period =

1 ÷ [(1 ÷ 365.25636) + (1 ÷ 583.9205)] = 224.70067 Earth days.  

Mars’ orbital period =

1 ÷ [(1 ÷ 365.25636) MINUS (1 ÷ 779.9382)] = 686.9782 Earth days.

(Note:- The MINUS here is because Mars is a superior planet!)