title: Mistakes when extracting date from datetime using as.Date function
body: <p>I need to get date from datetime, I used as.Date function</p>
  <p>2016-11-04 15:12:00 --- 2016-11-04  -- true</p>
  <p>2018-03-17 19:18:00 --- 2018-03-18  -- false, it should be 2018-03-17</p>
  <p>I noticed when the time is greater than &quot;17:00&quot;, the date is added 1 day. What is the reason? Is there a better way to get correct date?</p>