An example of how to limit the Year question type, this will limit the selection to 1964 - 1994

example.php

<?php //Please do not include the opening PHP tag if you already have one 

function tw_year_range_early_range( $early_range, $year_qstn ) {
	return 53;
}
add_filter('FHEE__EE_SPCO_Reg_Step_Attendee_Information___generate_question_input__year_question__early_range', 'tw_year_range_early_range', 10, 2); 

function tw_year_range_end_range( $end_range, $year_qstn ) {
	return -23;
}
add_filter('FHEE__EE_SPCO_Reg_Step_Attendee_Information___generate_question_input__year_question__end_range', 'tw_year_range_end_range', 10, 2);