title: errno 22 when convering timestamp to date
body: <p>I am trying to convert the timestamp that I get from a ticker API to a human readable date.
  My code is below; can you please help me identifying what I am doing wrong?</p>
  <p>Thanks!!</p>
  <pre><code>import ccxt
  from datetime import datetime
  from datetime import timezone
  import pytz
  kraken = ccxt.kraken()
  kraken_price = kraken.fetch_ticker('BTC/USD')
  kraken_time = kraken_price['timestamp']
  kraken_date = datetime.fromtimestamp(int(kraken_time)).strftime('%y-%m-%d %H:%M:%S')/1000
  print(kraken_date)
  print('Ask price for Kraken ${}'.format(kraken_price['ask']))
  </code></pre>
  <p>P.S. I am doing this in python</p>