Chandra (Moon) mahadasha for Mithuna (Gemini) Moon sign

In the Vimshottari system a life moves through nine long periods, each ruled by one planet. The planet that rules the period sets the tone of those years: the areas of life that come forward, and the kind of effort that pays.

The Moon mahadasha lasts 10 years in full. Most people meet it partway through, so the part they live through can be shorter.

The Moon stands for the mind, feelings, the mother and home. Its period tends to make family, comfort and moods more central, and brings more contact with people and the public.

Counted from Gemini as the first house, Moon rules Cancer, your 2nd house. During its period the matters of that house come forward:

The 2nd house is money, savings, speech and family. Its lord's period tends to bring attention to earning and saving, to what you say and how, and to the family you live with.

Moon counts Mercury, the lord of Gemini, as a natural friend. That usually makes its period sit comfortably with your Moon sign: its themes arrive with support rather than friction.

Which mahadasha you are in, and when it began, depends on the Moon's nakshatra at the moment you were born, so it is personal to you. Even within the Moon mahadasha, where the planet sits in your own chart and the sub-periods inside it shape the years more than your Moon sign alone.