Change the return format for date and time in lookup field.

lookupformat.php

<?php

add_filter( 'frm_filtered_lookup_options', 'format_date_display', 10, 2 );
function format_date_display( $options, $args ) {
  if ( $args['field']->id == 31427 ) { // change 20116 to the ID of the date field in the other form
    foreach ( $options as $k => $option ) {
		$option =new DateTime($option);
		 $options[$k]= date_format($option,"m/d/Y");;
    }
 }
 return $options;
}

add_filter( 'frm_filtered_lookup_options', 'format_time_display', 10, 2 );
function format_time_display( $options, $args ) {
  if ( $args['field']->id == 31428 ) { // change 31428 to the ID of the time field in the other form
    foreach ( $options as $k => $option ) {
		
		 $options[$k]= date("h:i a",strtotime($option));
    }
 }
 return $options;
}