Apple has just released its Second Quarter Results. They appear to define their "second" quarter (Q2) of 2021 as ending at the end of March, and their "first" quarter (Q1) of 2021 as ending at the end of the previous year i.e. December 2020.
Why do they define their quarters to be three months ahead? Is there a particular benefit in doing it this way? I would expect Q1 to be January-March and Q2 to be April-June. Additionally, is this something they have chosen to do, or is this a regulation that they have to adhere to?