The story relating to the different stages and landmarks in the evolution of our national flag is indeed inspiring:

The historic dates and landmarks are:

1906: Three colours: Saffron with eight stars across, white with Vande Mataram and green with moon to right and sun to left. This flag was proposed by some Indians in England and France who thought of an ‘Indian National Flag’. Not recognised in India.

1916: Two colours: Red and green, with five red and four green stripes. Emblem of Great Bear. Union Jack at top left. In vogue during ‘Home rule days’.

1921: Three colours: White, green and red, with Charkha across all colours. Sponsored by Mahatma Gandhi at the Bezwada Session of the Indian National Congress (this flag was informally used at all sessions of the Congress till 1931, though not officially accepted/adopted by the Congress).

March, 1931: One colour: Saffron with Charkha at top left. This flag was proposed by a committee appointed by Working Committee after Karachi Congress. This flag was not approved by Working Committee.

August, 1931:Three colours: Saffron, white and green, Charkha in blue colour in middle across white strip. Length and breadth in proportion of 3:2. Proposed by Congress Working Committee. Form of Flag suggested by Mahatma Gandhi retained with slight changes in order of colours and position of Chakra. Accepted by AICC officially in Bombay in August 1931.

August 15, 1947: The present tricolour National Flag was adopted.

Note: The source could not be confirmed. I bear no responsibility in the accurateness and correctness of the text mentioned above.

If anyone can provide me with some official links, please do so. I would be happy to link to the official website or sources.