title: Convert fraction of day to POSIX times in R
body: <p>I have a dataset that encodes a date-time into two separate variables.  Normally, I'd just paste them together inside of an <code>as.POSIXct</code> and carry on.  However, the date is provided as a string, and the time of day as a fraction of 24 hours - e.g., 12pm is 0.5, 9:30am is 0.1458333, etc.</p>
  
  <p>It doesn't seem all that tricky to convert the fractional days into clock hours, but I'd prefer to use a pre-existing function if possible.  Does something like that exist in base R?  A package?</p>
  
  <p>If it's any use, this is an Excel (xlsx) time field imported into R through RODBC.</p>
  
  <p>EDIT
  Oddly enough, upon revisiting this problem, the times are now read in as POSIXct.  Not sure what to make of that.</p>