Surya (Sun) mahadasha for Simha (Leo) 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 Sun mahadasha lasts 6 years in full. Most people meet it partway through, so the part they live through can be shorter.

The Sun stands for authority, confidence, the father and people in charge. Its period tends to bring questions of position and recognition, a wish to lead or to be seen for what you do, and dealings with seniors and public bodies.

Counted from Leo as the first house, Sun rules Leo, your 1st house. During its period the matters of that house come forward:

The 1st house is you yourself: your direction, confidence and the way you meet the world. Its lord's period tends to put you at the centre of your own story and to favour fresh starts you choose for yourself.

Sun is itself the lord of Leo. Its period tends to feel close to your own nature, and what it brings is usually easier to own and make use of.

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 Sun mahadasha, where the planet sits in your own chart and the sub-periods inside it shape the years more than your Moon sign alone.