title: Dealing with timestamps in R
body: <p>I have multiple lists of measurements. In each list have the timestramp formated as a string ("2009-12-24 21:00:07.0") and I know that each measurement in the list is separated by 5 seconds.
  I want to combine all data into a huge data.frame in R. Afterwards I want to be able to easily access the time difference of two measurements so I probably should convert data into something different than characters.</p>
  
  <p>Which format should I use to store the times? Is there some time format in some package that I should use?</p>