Sade Saathi = 7.5 years Saturn transit
Saturn takes 7.5 years to cross 3 signs. ie. the sign in which your moon is at birth, the previous one and the next one. (sign means raashi)

eg. If moon is in Taurus in your horoscope then you have Sade Sathi Saturn when Saturn is in Aries, Taurus or Gemini.

So what? Saturn always causes delay, problems, loss, learning lessons on how cruel the world is. To mitigate the suffering both mental and financial, propitiate Saturn.

Visit to Hanuman temple every Saturday is strongly recommended. Participating in Saturn Transit time poojas is desirable. Visiting temples where Saturn idol is present is good. Daily recite Dasharatha Maharaja Krita Shanaishwara Stotra during this 7 and a half years.