What is Sade Sati?
Sade Sati is the seven-and-a-half year period during which Saturn transits the 12th, the 1st and the 2nd house from your natal Moon. Saturn spends roughly two and a half years in each sign, which is where the name comes from. It is not a punishment - it is a period that strips away what was never solid and rewards patient, honest work.
The three phases
The rising phase, with Saturn in the 12th from the Moon, tends to press on expenditure, sleep and family matters. The peak phase, Saturn over the Moon itself, is felt most directly - health, reputation and workload. The setting phase, Saturn in the 2nd, eases but asks for care with money and speech. Shani Dhaiya, Saturn in the 4th or 8th from the Moon, is a separate two-and-a-half year period and is reported separately here.