Calculus is around 350 years old. Newton developed it in his twenties. Which was in 1660.
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He started learning calculus when he was around twelve years old and had mastered it by the age of 15.
Calculus; by a long shot.
Just about all of calculus is based on differential and integral calculus, including Calculus 1! However, Calculus 1 is more likely to cover differential calculus, with integral calculus soon after. So there really isn't a right answer for this question.
According to Wikipedia, his main manuscript on calculus, which he called fluxions, was published in October, 1666. He was 2 months short of 24 years of age at the time.
It is certainly used in calculus, just as calculus can be used in trigonometry.