function set_period()
{
	var today = new Date();
	var current_year = today.getFullYear();
	var span_date = document.getElementById('copy').getElementsByTagName('span')[0];
	var release_year = parseInt( span_date.innerHTML );

	if ( current_year > release_year ) {
		span_date.innerHTML = release_year + '—' + current_year;
	}
}

window.onload=set_period;