title: Read Excel file in R with multiple date format
body: <p>I'm trying to read an Excel file in R, with two columns containing dates. Now here is my problem, when I view my data file in R, most of the dates are in the good format, but some were transformed into number that don't make sense at all. I joined images to show the different outputs from R/Excel. </p>
  
  <p>(Only pay attention to the columns "ArrivalDate" and ActlFlightDate")</p>
  
  <p><a href="https://i.stack.imgur.com/PeG1b.png" rel="nofollow noreferrer">Output seen from R</a></p>
  
  <p><a href="https://i.stack.imgur.com/EASrG.png" rel="nofollow noreferrer">Output seen from Excel</a></p>
  
  <p>My question is, how, in R, can I make those numbers become the date they are supposed to be? Especially since the class of the elements in those columns are characters. </p>
  
  <p>Thank you in advance! </p>