A more thorough explanation:

Definition: The onset date is the start of a period of disability that is used to determine disability payments by the Social Security Administration.

Example: John was injured in a car accident on January 1st, 2020. He was unable to work due to his injuries and applied for disability benefits. The Social Security Administration determined that his onset date was January 1st, 2020, and he began receiving disability payments starting from that date.

Explanation: The example illustrates how the onset date is used to determine when a person's disability began and when they are eligible to receive disability payments. In this case, John's onset date was the day he was injured and unable to work, which is when his period of disability began.