Calculus may seem by now a completely mature topic, but nothing could be further from the truth. Calculus is growing in the number of people that study it across the world, it is being absorbed at an ever younger age, and it is being used because of the power of models across an ever-expanding range of disciplines. The calculus functionality in the Wolfram Language, already the the strongest in the world, improves dramatically in Version 12. New calculus topics are automated, existing functions are strengthened and the whole subsystem is re-engineered for learnability and applicability.