But Feburary doesn't have 29 days except once every four years, so trying to "hard code" that value for every year will not produce the correct date 3 years out of 4. Surely the 28 works for all years that are not leap years?
Date ( 3 ; 0 ; SpecifydesiredYearHere )
will produce a valid date for the last day of February, either 29 for leap years and 28 for years that are not leap years.
Note that this method can compute valid dates for the last day of a month regardless of whether that month is 28, 29, 30 or 31 days in length.