title: What does the lubridate note "method with signature ‘Timespan#Timespan’ chosen for function ‘%/%’" mean?
body: <p>When I run the following code in R I get a strange note (it only appears the first time I run the code in a session):</p>
  
  <pre><code>&gt; library(lubridate)
  Attaching package: ‘lubridate’
  The following object is masked from ‘package:base’:
      date
  Warning message:
  package ‘lubridate’ was built under R version 3.3.2 
  &gt; data.frame(i = interval(ymd(20140101), ymd(20160101)))$i %/% years(1)
  Note: method with signature ‘Timespan#Timespan’ chosen for function ‘%/%’,
    target signature ‘Interval#Period’.
    "Interval#ANY", "ANY#Period" would also be valid
  [1] 2
  </code></pre>
  
  <p>I am doubly confused:</p>
  
  <ol>
  <li>I am unclear as to what the alternative syntax is that it is
  recommending. A # is a comment in R, so presumably the hash is meant
  to mean something other than a hash, but what? </li>
  <li>Is it telling me I am doing something wrong? The note seems to suggest it is    an FYI, but an FYI is an odd thing to be spat out of a function if there is no problem.</li>
  </ol>