DATE
Returns a date string corresponding to day number.
Syntax
DATE(Value)
Value is an integer or a formula which
returns an integer. Day number 1 corresponds to January 1st, 1960. Negative numbers
correspond to prior years. The date strings returned have the yy-mm-dd format. Years in the
21st century through the year 2059 are represented by the numbers 00 through 59.
Example
This example returns '61-12-31':
DATE(731)
This example returns '14-10-03':
DATE(20000)
Non-integer numbers specified as arguments to this function are rounded up to the next integer.