DATE(year, month, day)
returns the date, expressed as a date-time serial number. year is an integer between 1583 and 9956 or between 0 and 99; month and day are integers.
If month and day are not within range for a valid date, the date will 'roll over', as shown below.
DATE(2021, 11, 9)
returns the date 9th November 2021 (as a date-time serial number).
DATE(2021, 12, 32)
returns 1st January 2022 - the date rolls over, as 32nd December 2021 is not valid.
DATE(2004, 3, 0)
returns 29th February 2004 - the date rolls over backwards, as 0th March 2004 is not valid. 2004 was a leap year.
DATE(2021 15, 8)
returns 8th March 2022 - the date rolls over, as there are only 12 months in a year