start_time and end_time will not set

If I change the start_time and end_time from the default "0" setting -- then click to add event comes up blank (also reloading main page comes blank)

e.g
$ltw_config['start_time'] = 08:30:AM;
$ltw_config['end_time'] = 05:30M;

Would someone prived actual example of correct syntax

Running 4.2.1

Safest bet is to use 24-hour format

$ltw_config['start_time'] = 08:30:00;
$ltw_config['end_time'] = 17:30:00;