[FreeLander]

А в чём проблема?

new Date()
new Date(year, month [, date [, hour [, minute [, second [, millisecond ]]]]])

Parameters
year A value of 0 to 99 indicates 1900 though 1999; otherwise all four digits of the year must be specified.

month An integer from 0 (January) to 11 (December).

date An integer from 1 to 31. This parameter is optional.

hour An integer from 0 (midnight) to 23 (11 p.m.).

minute An integer from 0 to 59. This parameter is optional.

second An integer from 0 to 59. This parameter is optional.

millisecond An integer from 0 to 999. This parameter is optional.

парсишь данные из инпута, преобразуешь их в тип Нумбер и пихаешь в свой объект.

new Date()
var year:String = "2004"
var myDate: Date = new Date(Number(year), 4 , 3 , 12 , 4 , 10, 100);
trace (myDate);