The 120-year clock
Vimshottari Dasha divides life into nine planetary periods totalling 120 years. Your starting point is determined by the moon's nakshatra at birth.
Career-favourable dashas
Look at the dasha lord's relationship to the 10th house, 10th lord, and the Sun (king-significator).
A worked example
A Jupiter mahadasha when Jupiter sits in the 10th can deliver leadership opportunity; the same Jupiter in the 8th may deliver internal restructuring instead.