const angle = (time = '00:00') => {
  let [hour, minute] = time.split(':').map(v => parseInt(v, 10));
  hour += minute / 60;
  let ah = (360 / 12) * (hour % 12);
  let am = (360 / 60) * minute;
  let diff = Math.abs(ah - am);
  return diff > 180 ? 360 - diff : diff;
};

[
  '00:00', '12:00', '00:30',
  '01:00', '13:00',
  '02:00',
  '03:00',
  '04:00',
  '05:00',
  '06:00', '06:30',
  '07:00',
  '08:00', '08:20',
  '09:00',
  '10:00',
  '11:00',
].forEach(v => console.log(v, angle(v)));