In the natal chart lets suppose the moon is placed in the zodiac sign of Libra (please see the diagram below). Then during the transit(gochar) of Saturn, when Saturn enters the sign of Virgo then the first stage of ‘Sade-Sati’ starts. Now, Saturn takes 2.5 years to transit through Virgo and then it enters into the sign of Libra where it stays for another 2.5 years before proceeding to Scorpio where it transits for another 2.5 years. This entire stint of 2.5 years in Virgo to 2.5 years in Libra and finally 2.5 years in Scorpio adds to 7.5 years and this is called as ‘Sade-Sati’.
For a native whose Saturn is ill-placed in the natal chart suffers much during this transit of Saturn for 7.5 years and it called as the phase of ‘Sade-Sati’.
Therefore the generalized definition of ‘Sade-Sati’ is as follows- ‘When transiting Saturn enters the sign preceding the zodiac sign in which Moon is placed in the natal chart to the Zodiac sign in which Moon is placed in the natal chart to the Zodiac sign immediately succeeding the zodiac sign in which Moon is present is called as the phase of ‘Sade-Sati’.
Uttarayan’ is generally considered auspicious and legends say it that Bhishma, who had been granted the boon of immortality, decided to leave for the heavenly abode post the Mahabharat war on the first day of ‘Uttarayan’ as it was auspicious.
Similarly, ‘Dakshin’ means South and ‘Ayan’ means movement. Essentially, ‘Dakshinayan’ is the Southward movement of the sun starting from the point when it enters the sign of Cancer on ‘Kark Sankranti’ (which falls on 16th of July every year) to the Winter Solstice i.e. on December 22nd of every year.
During ‘Dakshinayan’ the Sun’s journey starts when it enters in the zodiac sign of Cancer (on ‘Kark Sankranti’) and then moves on to the sign of Leo to the sign of Virgo and then to the sign of Libra followed by the sign of Scorpio and finally into the zodiac sign of Sagittarius. ‘Dakshinayan’ is generally considered inauspicious.
Please note:- When we say the movement of the Sun it means the apparent movement of the Sun as seen from earth since it is the earth that orbits around the Sun in elliptical path and not the other way round.