Date and Time
This function calculates a date specified by year, month, day and displays it in the cell's formatting. The default format of a cell containing the DATE function is the date format, but you can format the cells with any other number format.
DATE(Year; Month; Day)
Year is an integer between 1583 and 9957 or between 0 and 99.
In Tools > Options > LibreOffice > General you can set from which year a two-digit number entry is recognized as 20xx.
Month is an integer indicating the month.
Day is an integer indicating the day of the month.
If the values for month and day are out of bounds, they are carried over to the next digit. If you enter =DATE(00;12;31) the result will be 2000-12-31. If, on the other hand, you enter =DATE(00;13;31) the result will be 2001-01-31.
=DATE(00;1;31) yields 1/31/00 if the cell format setting is MM/DD/YY.