hadley/lubridate — pull request #102 by Vald (2011-12-02 09:00:20+00:00)
Title: 'c.period' and 'as.interval'

Small adjustement in the 'c.period' method. This allow
to combine period with list and data.frame without any
cast.

and

The calculation of 'day.no' is time consuming, especially
when working with thousands of intervals. A test is added
in order to do this calculation only if needed to optimize time
calculation.