Rather than asking only where the planets are moving through the sky now, Dashas provide a personalised timeline calculated from your birth chart.
One of the best-known systems is Vimshottari Dasha.
It divides a 120-year mathematical cycle among nine planetary influences, with your starting point determined from the position of your Moon within its birth Nakshatra.
A Dasha can indicate that particular parts of your natal Vedic chart are receiving greater emphasis during a chapter of your life.
It does not guarantee that one particular event will occur.