Perjury

The intentional act of swearing a false oath, whether spoken or in writing, concerning matters material to an official proceeding. Contrary to the popular misconception, no crime has occurred when the false statement is made under oath. Criminal culpability only attaches at the instant the false statement has a material outcome to the proceedings.

For example, it is not perjury to lie under oath in court about your age, except where your age is material in influencing the outcome of the proceedings.