function saveOptions() {
	var timeformat;
	if (document.getElementById('t24').checked)
		timeformat = 24;
	else if (document.getElementById('t12').checked)
		timeformat = 12;
	else
		return;

	localStorage['timeformat'] = timeformat;

	var status = document.getElementById('status');
	status.innerHTML = 'Options saved';
	setTimeout(function() { status.innerHTML = '' }, 2000);
}

function restoreOptions() {
	// default to 24 for both unset and invalid
	var timeformat = localStorage['timeformat'] || 24;
	var option = document.getElementById('t' + timeformat) ||
		document.getElementById('t24');

	option.checked = true;
}

function startOptions() {
	restoreOptions();

	document.querySelector('#save').addEventListener('click', saveOptions);
}

window.onload = startOptions;