title: How to subtract/add days from/to a date?
body: <p>I'm trying to build folders to store data pulls. I want to label the folders with the day of that data in the pull.</p>
  
  <p>Ex. I pull 5 days ago data from mysql i want to name the folder the date from 5 days ago.</p>
  
  <p>MySQL can easily handle date arithmetic. I'm not sure exactly how R does it. Should i just subtract the appropriate number of seconds in POSIXct and then convert to POSIXlt to name the folder MM_DD_YYYY?</p>
  
  <p>Or is there a better way?</p>