title: How to convert R Date into Excel numeric serial date?
body: <p>Excel stores dates internally as floating-point serial date. We know how to convert it into R - using <code>as.Date(var2, origin="1899-12-30", tz='UTC')</code>. </p>
  
  <p>The question is: <strong>how to convert it back into Excel</strong>? I tried all the obvious things, but I still get a mismatch.</p>