How To Show Last Modified Date On Blog Post Instead Of Published Date in WordPress

// Post Date Function

function post_date(){

	// If modified date

	if ( get_the_date() !== get_the_modified_date() ) {

		$dateTime = get_the_modified_date( 'c' );

		$itemropType = 'dateModified';

		$date = '<span>'. get_the_modified_date() .'</span>';

	} else { // If published date

		$dateTime = get_the_date( 'c' );

		$itemropType = 'datePublished';

		$date = '<span>'. get_the_date() .'</span>';

	}

	return '<time class="date" datetime="'.$dateTime.'" itemprop="'.$itemropType.'">'.$date.'</time>';

}

// Display - echo function 

echo post_date();