Functions to work with date-times and time-spans: fast and user
  friendly parsing of date-time data, extraction and updating of
  components of a date-time (years, months, days, hours, minutes, and
  seconds), algebraic manipulation on date-time and time-span objects.
  The 'lubridate' package has a consistent and memorable syntax that
  makes working with dates easy and fun.

  WWW: https://cran.r-project.org/web/packages/lubridate/