After "It's time" it is traditional to use a verb in the past tense form. This is sometimes called the subjunctive. It is called an idiomatic expression by other linguists. Examples: It's time you were in bed. It's time you went to bed. It's time we told your mother. It's time your father was told. A tale/story OF something. The -of- is similar to -about-. This is the story of John Bunyan. This is the story about John Bunyan. 'This is the story of how you took a child and made him old' is similar to 'This is the story about how you took a child and made him old'. English uses 'of' in many different ways.