This equation will calculate the date given the 3 variables you specified
In Years( :year - 1904 ) + In Weeks( :week of the year ) + In Days( :day of the week )
This equation assumes the week of the year begins on January 1. If your data has a rule for what day the week of the year begins, like the first Sunday of the year that offset will have to be calculated and then added to the formula.
Jim